Analysis of high polymers - Analytical Chemistry (ACS Publications)

Analysis of High Polymers John G. Cobler' and Carl D. Chow2 The Dow Chemical Co., Midland, Mich. 48640

This survey includes analytical methodology related to polymer analysis that has appeared in the literature during the period between November 1974 and November 1976. The authors have attempted to review articles which will be most useful to the polymer analytical chemist. A valuable reference is the Polymer Handbook edited by Brandrup and Immergut in collaboration with McDowell(1). Fundamental constants and parameters relating to polymerization, solid state properties, and solution properties are tabulated. Physical properties of commercial polymers are also included. Specifications for plastics materials and test methods for analyzing commercial plastics are covered in publications of the American Society for Testing Materials (2, 3 ) . The Federal Food, Drug, and Cosmetic Act as amended ( 4 ) has spurred the development of regulatory methods for characterizing plastics and for determining plastics components extracted into food-simulating solvents and foods. Regulations pertaining to the use of plastics for food packaging and food contact applications and appropriate analytical methodology are published in the Code of Federal Regulations ( 5 ) .Examples of polymeric materials for which Food and Drug Administration regulations have been issued include: olefin polymers, nylon resins, polystyrene, polyurethane, vinyl chloride polymers, acrylonitrile polymers, epoxy resins, and urea-formaldehyde resins. The Food and Drug Administration has prepared an outline of recommended procedures to be followed and information to be included in petitions requesting issuance of regulations relative to the use of plastics materials for food packaging or food contact applications (6). GENERAL METHODS Acosta and Sastre ( A I ) reviewed the theoretical and practical aspects of determining monomeric compositions of polymers, using a methyl methacrylate-styrene copolymer as an example, by radioactive tracer techniques. Bello et al. ( A 3 ) reviewed the principles of polymer fractionation and presented tables of fractionation systems for various polymeric materials. Kuhn (A32) discussed the separation of approximately 30 different polymer blends, including graft polymers and copolymers, using solvent mixtures which were miscible a t high temperatures but showed phase separation a t lower temperatures. Methacrylic acid-styrene copolymers were fractionated according to molecular weight and chemical composition by precipitation with methanol from benzene solution (A17 ) . Methyl methacrylate-styrene copolymers were fractionated according to molecular weight by batch-wise and continuous column elution and by coacervation extraction techniques using different solvent-nonsolvent combinations ( A 3 4 ) . Solvent-nonsolvent systems such as ethylene carbonateethylene cyanohydrine and methyl ethyl ketone-cyclohexane were used for the fractionation of acrylonitrile-styrene random copolymers ( A 5 5 ) . Kalal et al. ( A 2 5 ) discussed the fractionation of vinyl chloride-vinyl acetate copolymers by precipitation chromatography employing precipitant-solvent systems such as acetone-methanol, acetone-heptane, tetrahydrofuran (THF)-water and THF-heptane. Ogawa and Inaba (A421 compared a computer simulation of the solution fractionation of ethylene-propylene copolymers with experimental results and showed that the products should be classified into five types: ethylene-propylene copolymer, polyethylene-polypropylene blends, polypropylene-copolymer blends, polyethylene-copolymer blends, and

Health and Environmental Research. Polymer Analysis, Analytical Laboratories

polypropylene-polyethylene-copolymer blends. Dimethylformamide (DMF)-alcohol systems fractionated polyurethanes such as 1,4-butanediol-diphenylmethane-diisocyanate copolymer and diphenylmethane-diisocyanate-polyethylene glycol adipate copolymer by chemical composition, whereas (Me2N)sPO-alcohol systems fractionated with respect to molecular weight (A48).Dimethylsulfoxide-alcohol systems also fractionated by molecular weight ( A 4 8 ) . The analysis and characterization of high impact polystyrene by chemical and spectral methods were reviewed by Hobbs et al. (A24).Hydrocarbon mineral oil was determined in impact polystyrene by Soxhlet extraction of the polymer with pentane followed by nuclear magnetic resonance (NMR) analysis of the extract to determine the amount of oligomers present (A411. Kranz and co-workers (A31) determined the structure of polybutadiene graft polymers from acrylonitrile-butadienestyrene (ABS) employing degradation techniques utilizing MesCCOOH-osmium tetraoxide. The polybutadiene was completely degraded without changing the degree of polymerization of the grafted acrylonitrile-styrene polymer chains. Acrylonitrile-styrene copolymer was separated from ABS graft copolymer by extraction with ethyl acetate (EtOAc) (A56).The ungrafted rubber was extracted from the insoluble portion with a 1:111, EtOAc-hexachlorobutadiene mixture. Roth (A47) determined the degree of cross-linking of dibutyl maleate-cross-linked butadiene-styrene copolymers by determining the temperature dependence of the dielectric loss factor and by a dye take-up procedure. Sodium methallylsulfonate in acrylonitrile copolymers was determined by using a colorimetric method with methylene blue ( A 3 7 ) . Analytical methods for the analysis of poly(viny1 alcohol) (PVA) were reviewed by Finch ( A 1 3 ) . Morishima and coworkers ( A 4 0 ) fractionated PVA according to the degree of short chain branching by foam fractionation. The authors also found that an increase in the amount of short chain branching units in PVA caused a decrease in the color intensity of the reaction of PVA with iodine. PVA was characterized by various physical and chemical methods before and after cleavage with NaI04 ( A 2 ) .NaI04 titrimetry was used to estimate the 1,2-glycol content. NMR spectroscopy and chemical analysis indicated that the major end-groups were HOCH2CH2- and CH&H(OH)CH(OH)CH2-. Pritchard and Fung (A45) determined glycolic 1,2-diol groups in styrene glycol and PVA by cleavage with K I 0 4 and determination of the excess periodate by titration with standard arsenite. The sodium acetate content of PVA was determined by measuring emf using a standard electrode containing neat PVA solution, a reference electrode containing PVA solution with 0.3%sodium acetate, and an indicating electrode containing the sample ( A 2 8 ) . Morishima and co-workers ( A 3 9 ) found that the shortest sequence of vinyl acetate required for formation of the iodine-poly(viny1 acetate) complex was approximately 12 monomeric units. The determination was based on gel permeation chromatography and spectroscopic studies of reduced chloroform-vinyl acetate telomer. Campbell ( A 8 ) determined combined vinyl acetate in vinyl acetate-vinyl chloride copolymers by an isotope dilution derivative method. The vinyl acetate was hydrolyzed with sodium hydroxide in methyl ethyl ketone in the presence of a known amount of 14CH3C02H.The resulting labeled sodium acetate was converted by reaction with o -CsH4(NH2)2 to labeled 2-methylbenzimidazole. The method was also used for the analysis of ethylene-vinyl acetate copolymers. Majer and Sodomka ( A 3 5 ) determined the vinyl acetate content in ethylene-vinyl acetate copolymers by hydrolysis in toluene with alcoholic KOH and back titration of the excess KOH with 0.1 N HC1. The authors also used an infrared method based on the absorbances of the infrared absorption bands at 610 and 720 cm-l. Hirai and Tanaka (A23) discussed the dependence of the iodine affinity of vinyl acetate-vinyl ANALYTICAL CHEMISTRY, VOL. 49, NO. 5, APRIL 1977

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propionate copolymers on the sequence distribution of vinyl acetate units. The analysis of poly(viny1 chloride) (PVC) was reviewed by Brookman ( A 7 ) ,Frissell ( A I 6 ) ,and Davis (AIO).Internal double bonds in PVC were determined by Michel et al. (A38), by low temperature ozonolysis. Vinyl chloride-vinyl bromide copolymers and butadiene-vinyl chloride copolymers were analyzed by ozonolysis at 0 to -20 OC. Above Oo, the polymers were degraded by autoxidation. Tanaka and Morikawa (A54), described a semimicro technique for the determination of total chlorine in PVC using a semimicro method based on the Schoeniger flask and Fajans method. The morphological and crystal structure of poly(methy1 methacrylate), polyethylene, polypropylene, and PVC were studied using a radioactive decay procedure (A20). The samples were kryptonated and the subsequent rate of spontaneous dekryptonation in air a t room temperature was related to the properties. Korosteleva and Dymarchuk (A30)used a high-frequency conductometric titration procedure to determine the degree of hydrolysis of polyacrylamide products. The concentration of carboxyl groups in hydrolyzed polyacrylamide was determined by conductometric titration of polymer solutions from which ammonium salts had been removed by precipitation with sodium tetraphenylborate (A49).Acrylamide monomer in polyacrylamide was determined by a differential pulse polarographic procedure by Betso and McLean ( A 5 ) . Crisp et al. (A91 employed a conductometric titration method to analyze polyacrylic acid and acrylic acid-itaconic acid copolymers. The authors found that a pH titration gave a readily detectable end point for the polyacrylic acid but a difficultly detectable end point for the copolymer. The 1,2 and 1,4 structures of polybutadiene, polyisoprene, and butadiene-propene copolymers were determined by Hackathorn and Brock (A19) by microozonolysis followed by gas chromatography. Ozonolysis of polybutadiene containing 1,4-1,2-1,4 sequences gave 3-formyl-1,6-hexanedial in direct proportion to the 1,2 content of the polymers. Ozonolysis of high 1,4-polybutadiene gave an unusual product, 4-octene1,8-dial. The ozonolysis of butadiene-propene polymers having an alternating structure yielded 3-methyl-1,6-hexanedial. Reed and Warren (A46) determined 2,6-di-tert -butyl-4methylphenol in polyolefins by thermal analysis-gas chromatography. Samples were analyzed in less than 30 minutes without solvent extraction. Foliforova et al. (A14) determined residual isocyanate and allophanate in thermoplastic polyurethanes based on the ability of the free cyano group to decompose in aqueous MezSO while the allophanate groups remain stable. Free and bonded cyano groups were determined by titrating MezSO solutions immediately with dibutyl amine. Bonded isocyanate groups were determined after the solutions had been allowed to stand in MezSO for a period of time before titration. Hydrazine- and 4,4-diaminodiphenylmethane-derivedterminal groups in urea-urethane polymers were determined by nonaqueous titration with perchloric acid in dioxane solution. Lithium chloride and acetic acid were added to increase the potential jump at the equivalence point (A12).A cooperative IUPAC study of the analysis of polyurethane resins was reviewed by O'Neill and Christensen (A43).Methods are given for the identification of isocyanates, polyols, and fatty acids and for the quantitative determination of isocyanate and dicarboxylic acid content of the resins. A colorimetric method for the determination of p-tertbutylphenol in bisphenol A polycarbonates employing diazotized p-nitroanaline was described ( A l l ) . Secondary amines of alkoxymethyl compounds of urea and melamine in urea-formaldehyde copolymers and melamineformaldehyde copolymers were determined based on a Mannich type reaction ( A 4 ) .Methods for the characterization of head-to-head poly(methy1 crotonates) and head-to-tail poly(methy1 transcrotonate) are described by Tanaka and Vogl (A53). Reviews have been published on the analysis of silicone monomers and oligomers (A50)and of silicone fluids, greases, resins, and elastomers ( A 5 1 ) .Trifunctional units, as impurities in poly(methylsiloxanes), were determined by reaction-gas chromatography using a mixture of NaHFz and oleum as the separating agent (A52).Khrustaleva and Bulatov (A27) de160R

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termined double bonds and vinyl groups in polysiloxanes containing isopropenylphenyl and methyl groups on each Si atom by bromination with Kaufmann reagent and thiocyanation. The excess reagent was determined by noncompensated potentiometric titration. Hydroxyl groups in epoxy and poly(oxypheny1ene) resins were determined by measuring the volume of hydrogen generated from reaction of hydroxyl groups with lithium aluminum hydride ( A 3 6 ) .Haszczyc and Walczyk (A21)developed a method for poly01 OH determination based on acylation with acid chlorides. The method is applicable to primary, secondary, and tertiary OH groups. King and co-workers (A29) determined polyester in cotton-polyester blend fabrics by dissolving the polyester in boiling monoethanolamine and weighing the cotton residue. Karchmarchik and co-workers (A26) determined the degree of imidization of poly(amido acids) from the concentration of free carboxyl groups as determined by titration and from the amount of water separated after heat treatment at 300 "C whereby 100% imidization occurred. Allylic double bonds in allyl monomers, oligoesters, and copolymers with fumaric oligoesters were determined by bromometric titration (A57).Double bonds were determined in prepolymers of diallylphthalate based on the reaction with mercuric acetate yielding As a by-product acetic acid which could then be determined potentiometrically ( A 6 ) . Frauenfelder (A15) reported a colorimetric-chromatographic method for the determination of poly(viny1 pyrrolidone) and its copolymers in food, beverages, laundry products, and cosmetics. Terminal amino groups in aromatic polymers were determined by Gerashchenko and co-workers (A18) using a colorimetric method based on reaction of the amine with p -dimethylaminobenzaldehyde. Kurenkov and coworkers (A33) determined sodium p-styrene-sulfonate polarographically either alone or in combination with acrylamide after conversion to the corresponding pseudonitrosite by treatment with sodium nitrite in acetic acid. The acrylamide content of the mixture was determined by direct polarography. Hen (A22) determined the concentration of acid bound at the surface of itaconic acid-styrene copolymer latexes and free acid in the water phase by conductometric titration. The concentration of acid bound within the latex particles was determined from the differences between the acid charge during polymerization and the conductometric titration data. The degree of activation of the surface of polyethylene film by corona discharge was studied. Best results were obtained by measuring the wetting tension of HCONH2-EtOCH2CH20H mixtures, one of which formed a stationary layer on the surface of the film and a second mixture which agglomerated into droplets (A44).

DETERMINATION OF INORGANIC CONSTITUENTS Henn ( B 2 ) reported on a flameless atomic absorption technique with solid sampling for determining trace amounts of iron, copper, and chromium in polymers such as polyacrylamide with a detection limit of approximately 0.01 part per million. Phosphorus was determined in thermally stable polymers by mineralizing the sample with a nitric acid-perchloric acid mixture and subsequent titration of the phosphate ions with La(N02)S or by ,photometric determination of the phosphomolybdic blue complex ( B 3 ) . Oguro (B4)extracted polypropylene with hydrochloric acid to remove antimony which was subsequently determined by atomic absorption spectrophotometry. Radovici et al. ( B 5 )reported on a polarographic method for the microdetermination of zinc in polyesters. The zinc content of chlorinated polymers was determined by fusing the sample with sodium peroxide followed by a standard complexometric titration of the resulting solution (Bl). GEL PERMEATION CHROMATOGRAPHY (GPC) Computer programs were written for G P C (C4l)-and GPC-viscosimetry to calculate the number (Mn),weight Mw),

John G. Cobler is an associate scientist with the Health and Environmental Research Department, Dow Chemical U.S.A. A graduate of the College of Wooster. where he received a B.S. in 1940, he did two years graduate study at Purdue University before joining the Pharmacology Division of the Manhattan Project. His Dow career began in 1949 in the Analytical Laboratories. In 1953, when he was promoted to group leader, he started the Polymer Analysis Laboratory and supervised its operation until 1969. He was named an associate scientist in 1969 and acted as a consultant in Dolymer analytical chemistry until 1975 when he transfekred to the Health and Environmental Research Department. He is currently responsible for government regulatory activities relating to the health safety of plastics materials. He has published 38 articles on polymer characterization and subjects related to the use of plastics materials for food and drug packaging applications. He is a member of the Division of Polymer Chemistry and the Division of Rubber Chemistry of the American Chemical Society, the Scientific Research Society of America, and the American Society for Testing Materials. At the present time he is chairman of the Methods Subcommittee of ASTM F-2 on Flexible Barrier Materials and chairman of the Analytical Methods Subcommittee of ASTM D-20 on Plastics. He has been active in technical subcommittees of the Society of Plastics Industry and the Manufacturing Chemists Association.

Carl D. Chow is a research specialist with the Polymer Analysis Group of the Analyticai Laboratories, Michlgan Division, The Dow Chemical Company. He received his B.S. in organic chemistry from the National Taiwan University and his M.S. in polymer chemistry from North Dakota State University. He joined the Physical Research Laboratory of Dow in 1965 and worked on polymerization kinetics, foam technology, and reinforced plastics He transferred to the Polymer Analysis Group in 1967. His specialities are molecular weight measurements, gel permeation ChromatoqraDhy(GPC), and thermal analysis. He has published in these areas and has lectured on GPC at local ACS sections and universities.

and 2 ( g z ) average molecular weights, dispersity index and the intrinsic viscosity (C42). MacLean reDorted an on-line data handline svstem for polymer molecdar weight distribution (MWD) andysis with high speed GPC (C25, C26). The imDortance of Dolvmer characterization bv GPC (C12. C13),theitate-of-the-ar-t of analytical GPC (Cl'b),methods and applications of GPC in the study of polymers (C16),and oligomers (C38)were discussed. The preparation, characterization, and application of a glycerolpropylsilane phase-bonded controlled pore glass was described (C35). Comparative evaluation of the bonded packing with uncoated packings for proteins, industrial glues, and poly(viny1 alcohol) was reported (C33). An aqueous system was used to characterize sodium (pplystyrene sulfonate) (C40).Interaction of the porous alumina packing with polyacrylamide was observed. GPC results obtained for sulfonated polystyrene agreed with those of viscosity measurements (C35). Styragel used as packing for aqueous GPC was demonstrated using 0.1% sodium lauryl sulfate aqueous solution as eluent. Chow was able to chromatograph dextrans on Styragel columns (C7). Kat0 et al. reported high speed, high resolution GPC for the analysis of MWD, oligomers, and plasticizers within 10 min~ gel (C20, C21).High performance utes using 5 - polystyrene GPC was achieved with highly porous trimethylsilylated silica beads (C43).Recent advances in preparative GPC were reviewed (C8,C9, C22). Polypropylene (C45)was fractionated with preparative GPC. The effect of concentration and sample size on polydispersity was discussed. A nitrobenzene-tetrachloroethane solvent system was developed for the MWD analysis of poly(ethy1ene terephthalate) a t room temperature. Advantages of this solvent over the

common solvent rn-cresol a t 110-135 "C were described and discussed ((240). An on-line infrared detector was used to determine compositional distribution of styrene copolymers ( C l l , C27). Molecular weight (MW) of styrene-maleic anhydride (MA) with MA content from 5-50 mol % was determined and found to be comparable to values obtained from the hydrodynamic volume calibration ((26). The degradation rates of polystyrene were determined by measuring the change in MWD by GPC and the amount of volatile materials. MW of acrylonitrile-ethyl vinyl ether polymers was determined by GPC in dimethylformamide (DMF)-lithium bromide (LiBr). The effect of LiBr on polymer-solvent behavior was studied (C23). GPC was applied to characterize the starting components and intermediates of polyurethane (C37, C44) and phenolic resins in DMF ((214, C l 5 ) . GPC in combination with viscometry and light scattering found great application in the study of branching in bisphenol-A polycarbonate (Cl ) polyethylene (PE),((239) poly(viny1 acetate), poly(viny1 alcohol) (C39)and other branched polymers (C31). The GPC of poly(1-butene sulfone) on Styragel using tetrahydrofuran as solvent was reported (C4). The determination of MWD of poly(viny1 chloride) and its copolymer by GPC, especially the problems of calibration and effect of aggregates, was reviewed (C19). The use of GPC to determine total polymer content in comdex comDonents without Drior seDaration was demonstraied (C18): The MW study of epoxide resins with GPC (C2, C3) or combination of GPC and liquid chromatography (C46)was reported. GPC was used to study MW of P E oligomers with polyurethane gel and T H F as solvent (C24) and low density P E with a new mathematic data interpretation (C5). Linear P E was fractionated to narrow MWD with MW range of 1500800 000; the characterized fractions are commercially available according to the authors (C34).

THERMAL ANALYSIS (TA) Thermal analysis (TA) techniques and applications of TA for research in the field of coatings and polymers were discussed ( 0 7 , D l l , 0 4 2 ) . Data were presented to illustrate the advantages of differential scanning calorimetry (DSC) as a substitute for ASTM D-789 for determining polymer melting behavior ( 0 1 8 ) .TA has found applications for quality control of polymers ( 0 4 , 0 1 9 ) . Use of differential thermal analysis (DTA) to identify poly(viny1 chloride), polyethylene, polypropylene, poly(methyl methacrylate), polycarbonate, polyamides, polyesters, polyurethanes, epoxy resins, and phenolic resins and their variations was demonstrated ( 0 3 ) . TA was used to study the miscibility of a fire retardant in acrylonitrile-butadiene-styrene (ABS) copolymers, and its effect on the impact and flexural strengths ( 0 1 ) . An optimum molecular weight was observed for the maximum thermal stability of poly(viny1 acetate) but not of poly(viny1 alcohol) ( 0 5 0 ) . The functional dependence of the kinetic parameters on molecular weight of polystyrene was studied by thermal volatilization analysis. This dependence was previously unobserved ( 0 3 4 ) . An empirical relation equation was derived to show the dependence of glass transition ( T ) of vinyl polymers with side chain of various lengths ( 0 2 7 , b28). Reactivity ratios and compositions of propylene-tetrafluoroethylene, isobutylene-tetrafluoroethylene, and ethyl acrylate-vinylidene chloride were calculated and discussed in terms of glass and melting transitions (D5,0 8 ) . The use of TA methods to study T , was discussed in numerous publications; poly(ethy1ene terephthalate) by thermal mechanical analysis (TMA) ( 0 3 5 ) and DTA ( 0 3 7 ) , poly(methyl methacrylate) and polycarbonate by DSC, (017 ) , polystyrene by DTA and torsional braid analysis (TBA) (020, 023,045). The dependence of T , on molecular weight of low polydispersity polystyrene was studied using DSC ( 0 2 , 0 4 9 ) . The effect of sequence distribution on T , of acrylonitrileANALYTICAL CHEMISTRY, VOL. 49, NO. 5, APRIL 1977

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methyl methacrylate, acrylonitrile-methyl methacrylatecu-methylstyrene copolymers was studied. The T , of copolymers was predicted using a comonomer sequence distribution-T, relationship (029).A statistical method for determining T , from dilatometric data using the technique of fitting a segmented linear regression model was proposed. The application to poly(ethy1ene terephthalate) fiber was demonstrated ( 0 6 ) .

TORSIONAL BRAID ANALYSIS (TBA) Mechanical data to study the friction characteristics of polyimide films bonded to metallic substrates was obtained by TBA (016).TBA was used to study the structure-property relation of polyimide ( 0 2 1 ) and the thermal degradation of polymethacrylates, polyacrylates, poly(viny1 alcohol) (015). Two transitions occurring in thermosetting process of an epoxy system were demonstrated by TBA (022). THERMOGRAVIMETRY (TG) The assembly and operation of a directly coupled thermal balance and quadropole mass spectrometer system were described. Examples using polyurethanes, acrylonitrile-butadiene-styrene (ABS) plastics and polyesters were given to illustrate the usefulness of the method ( 0 3 6 ) .The effect of chemical structure of polyimides on their thermal stability was studied by T G ( 0 3 2 ) . The thermal stability of oligoester was related to the strength of the acid and length of the glycol ( 0 1 2 ) .The thermal degradation of poly(ethy1ene terephthalate) (PET) (041), and vinyl acetate copolymers ( 0 4 7 ) was investigated. The kinetics of the P E T degradation were affected by diethylene glycol content and catalyst system. DIFFERENTIAL THERMAL ANALYSIS DTA measurements on sharp melting, low-molecular weight compounds confirmed that the melting point of polymers was proportional to the square root of heating rate, heat of fusion, and sample mass. The true melting points of crystalline polyethylene and nylons were determined ( 0 2 6 ) .The effect of heating rate and degree of cross-linking on the melting point of poly(viny1 alcohol) was noted ( 0 3 8 ) .Differential scanning calorimetry (DSC) was used to study the crystal structure and thermal stability of poly(viny1 alcohol) modified at low levels by various reagents and by grafting with other vinyl monomers ( 0 4 8 ) .DSC was also used to study the degree of crystallinity of nylon 6 ( 0 9 , 0 3 0 )and cross-linked poly(viny1 alcohol) hydrogels submitted to a dehydration and annealing process (039).The development of crystal modifications of poly-1-butene was followed using DSC ( 0 1 3 ) . A kinetic study of isothermal cure of epoxy resin was carried out (043,044),with DSC. Kinetic parameters associated with the cross-linking process of formaldehyde-phenol, and formaldehyde-melamine copolymers was obtained from exotherms of a single DSC temperature scan ( 0 3 1 ) . The heat of volatilization of polymers was determined by DSC. Values obtained for poly(methy1 methacrylate) agreed well with calculated values ( 0 1 4 ) .The differential thermal analysis (DTA) curve of amorphous poly(ethy1ene adipate) was explained and interpreted (046). Oxidative exotherms of untreated and processed polyethylene were recorded. Addition of stabilizers shifted the exotherm to higher peak temperature. The activation energy for the thermal decomposition was reported ( 0 4 3 ) .DTA study of ethylene copolymers showed a decrease in melting point as the length of side chains increased ( 0 2 4 ) .Chemically crosslinked and oriented low-density polyethylenes were investigated using thermal optical analysis and DSC ( 0 2 5 , 0 4 0 ) . ELECTRON SPECTROSCOPY FOR CHEMICAL ANALYSIS (ESCA) Clark discussed and reviewed the applications of ESCA to study the structure and bonding in polymers (E3-E6). ESCA was used to characterize fluorine-containing polymer films for degree of crystallinity and adsorbed gas content (E1). Valence bond structures of many polymers were revealed by ESCA (E7, E8). 162R

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ESCA was found to be suitable to establish a comprehensive picture of the early stages of the fluorination process of polyethylene (E2).

GAS CHROMATOGRAPHY Headspace methods for the determination of residual monomers and volatiles in polymers were reported by Steichen (G31) and by Shanks ((230).Steichen determined residual vinyl chloride, butadiene, acrylonitrile, styrene, and 2-ethylhexyl acrylate in polymers with an analytical sensitivity of 0.05 to 5 ppm by analysis of the equilibrated headspace over polymer solutions. Shanks determined acrylonitrile, a-methyl styrene, and styrene monomers by headspace analysis over heated solid polymer samples. Szymczak et al. (G33) determined the concentration of caprolactam in aqueous and organic solutions b y extraction with chloroform and subsequent gas chromatographic (GC) determination. Water was determined in polymers such as nylon 6 by heating the polymer at a temperature in excess of 120 "C (G7).Absorption of the water in an absorbent such as barium chloride was followed by desorption and GC determination of the desorbed water. The hydrolysis products of methyl cellulose and ethyl cellulose were converted to the corresponding sorbitol ethers and then acetylated to give products readily separated by GC (G13). Aliphatic dicarboxylic acid esters such as adipates, sebacates, and azelates were analyzed by coupling thin-layer chromatography with programmed GC (G3).Oprea and Pogorevici (G25) reported on the GC determination of ethylene glycol, dimethyl terephthalate, dimethyl isophthalate, and dimethyl adipate in ethylene glycol-isophthalic acid-terephthalic acid copolymers and in adipic acid-ethylene glycol-terephthalic copolymers. Tsarfin and Kharchenkova (G34)reported on a GC method for the determination of diethylene glycol, glycerol, and trimethylolpropane in complex polyesters. Resole polyesters were analyzed after treatment with excess sodium sulfite at pH 9.9, to prevent hemiformal formation, followed by drying and acetylation with acetic anhydride-pyridine. The acetylated resole components were analyzed by GC ( G 8 ) . Mlejnek and Cveckova (G20)measured the hydrazinolysis and Me4NOH aminolysis products of polyamines, polyimides, polyurethanes, polyesters, alkyd resins, and epoxy resins. The reaction with Me4NOH was more universal than other reactions. Chain transfer agents such as acetic acid and propionic acid used in the polymerization of polyamide-6 were determined by GC analysis of hydrolysis products (G32). Pyrolysis-gas chromatographic (PGC) techniques for the analysis of polymers were reported by a number of investigators. Grassie (G10)reviewed the present trends in polymer degradation. Waysman (G39) determined the chemical and structural differences in epoxy resins by GC of the volatile products formed by pyrolysis of the resin samples at 800 " C for 7.5 seconds. Temperature-programmed pyrolysis and subsequent detection of the pyrolysis products by mass spectrometry (MS) was employed to identify the products of decomposition and determine the kinetics of formation of epoxy resins (G15).Probsthain (G26)found that pyrolysis of cross-linked phenol-formaldehyde polymers resulted in cleavage of the bridges between the rings, forming phenol, 0 - , and m-cresol, 2,4,6-trimethylphenol. Isobe and Nakajima (G12)pyrolyzed cellulose triacetate at 450 "C and determined the amount of acetic acid produced. The acetal content of the polymer determined by this method was in agreement with that determined chemically. Blasius and Haeusler ( G l )used PGC to estimate the degree of cross-linking, type of functional group, and position of substitution in styrene-divinylbenzene copolymer ion-exchange resins. Fingerprint spectra of ion-exchange resins obtained by pyrolysis-MS gave information on the type of Tutorskii and network and functional groups present (G2). co-workers (G37)employed data based on the PGC analysis of mixtures of polystyrene and polybutadiene to determine the distribution of polystyrene chains in butadiene-styrene block copolymers. Identification of dimer and trimer peaks of pyrograms was used to determine the sequence distributions in methyl acrylate-styrene copolymers (G36).Milina and Pankova (G19) determined the monomer compositions of acrylonitrile-methyl methacrylate copolymers by PGC.

The microstructure of acrylonitrile-vinyl chloride copoly. mers and methyl methacrylate-vinyl chloride copolymers was studied by Tanaka and Nishimura (G35) utilizing PGC techniques. Seeger et al. (G29) analyzed plasma polymerized polyethylene by flash pyrolysh combined with in-line hydrogenation and GC. The branch length and number of side chains in polyethylene was determined by Seeger and Barrall (G28) employing the aforementioned technique. The structure of a-irradiated 1,2-polybutadiene was studied using PGC-MS (G38).Nobel et al. (G23)characterized 179 glues and acrylic, cellulosic, epoxy, polyester, rubber, polystyrene, poly(viny1 acetate), and urea-formaldehyde resin adhesives by PGC supplemented by MS. The application was applied to both filled and unfilled samples. The relative contents of ethylene oxide and propylene oxide in polyethylene-polypropylene glycols was determined using combined PGC calibrated with polyethylene glycol and polypropylene glycol standards ((240). Nemirovskaya et al. (G21)attached a microreactor to a gas chromatograph to study the thermal oxidative degradation of polymers such as poly(dodecaneamide). Oxygen absorption and formation of volatile degradation products were simultaneously measured. Molecular probe GC techniques for the determination of glass transitions, melting temperatures, degree of crystallinity, compatibility, and interaction parameters were reported by a number of authors. Grozdov and Stepanov (G11) reviewed the use of the GC methods for determining solubility parameters of polymers. Solubility parameters obtained for poly(buty1 methacrylate) and polyisobutylene are given. A computer model for the GC behavior of polymer stationary phases was described by Braun, Lavoie, and Guillet (C5). The effects of operating conditions such as coating thickness, flow rate, and polymer properties on the computed retention diagrams were satisfactorily explained. Lichtenthaler and Prausnitz (GI 7 ) showed that the use of coated open tubular columns gave essentially the same results as packed columns when determining the polymer-solvent interaction coefficients. Schneider and Calugaru (G27)determined the glass transition temperature of poly(methy1 methacrylate) in blends with poly(viny1 chloride) (PVC). Although the glass transition temperature (T,) of the PVC remained constant, the T , of the poly(methy1 methacrylate) varied with composition, indicating some interactions between polymers. Braun et al. (G6) obtained a Z-shaped retention diagram on the GC of C4-16 normal alkanes and C8-10 1-alkanols on polystyrene, poly(methyl methacrylate), butadiene-styrene copolymer, and PVC a t a temperature just above the glass transition point. The behavior was considered diagnostic for T,, although the actual value corresponded most nearly with the onset of bulk sorption. The T , for isotactic polypropylene, syndiotactic polypropylene, add atactic polypropylene were determined using compounds which were solvents for the polymer for the second-order transitions; compounds having little solvent effect on the polymer were used to determine first-order transitions (G9). Inverse GC was found suitable for determining the crystallinity of olefin polymers where a linear extrapolation of density determinations was not applicable (G4). Crystallinity measurements were obtained on ethylene-vinyl acetate copolymer, carbon monoxide-ethylene copolymer, and on emulsifiable polyethylenes. Polymer compatibility and solvent-polymer interaction parameters were determined by Karim and Bonner ( G 1 4 ) ,Nesterov and Lipatov (G22),Olabisi ((2241,and by Marcille et al. (G18).The compatibility of polymers was determined by measuring the excess free energy and the enthalpy and entropy of mixing. Klein and Widdecke (G16) discussed the use of GC for characterizing synthetic polymers such as poly(ethy1ene oxide), polystyrene, and poly(viny1 acetate). Retention indexes were determined for benzene, ethanol, ethyl acetate, MeN02, and pyridine as polar test molecules. INFRARED AND RAMAN SPECTROMETRY Ivin (136) edited a book on the structural studies of macromolecules by spectroscopic methods. Tadokoro and KObayashi (179),Hummell (1351, Sastre and Acosta (172),and Derouault and Hendra (119)published reviews on vibrational spectroscopy for the study of high polymers. The far infrared spectra of polymers was reviewed by Rabolt (169).Reviews

on laser Raman spectroscopy as applied to polymers were published by Yu (190)and by Hendra (131). Holland-Moritz and Siesler (134) reviewed the application of infrared (IR) spectroscopy to the analysis of polymers. Read (170) reviewed the use of ultraviolet (UV), visible and infrared dichroism as applied to polymer characterization. Polarized fluorescence and Raman spectroscopy were reviewed by Bower (17). The application of Fourier Transform infrared (FTIR) spectroscopy to the study of polymeric materials was described by Coleman (113).A major area of interest to polymer scientists is the study of optically dense materials, taking advantage of the high energy throughput of the FTIR system. The molecular mechanics of single-chain deformation modes and multichain processes in terms of molecular stress and chain orientation distributions, bond rupture, and conformational changes were studied by dynamic IR analysis (188). Koberstein and co-workers (142) prepared thin uniform polymer films with random orientation, by a centrifugal casting technique, for use in transmission and dichroism measurements. Sodium chloride windows were used by Oberbeck and Mayhan (160) to determine time dependent changes in polymer films exposed to radio frequency plasma. The use of attenuated total reflectance (ATR) for quantitative analysis of polymers was discussed by Brunn and co-workers (18) using polymethylene, poly(methy1 methacrylate) and ethylene-methyl methacrylate copolymers as examples. Jasse and Monnerie (138)used IR and Raman spectroscopy in the region below 420 cm-l to characterize 2,4-diphenylpentane and 2,4,5-triphenylheptane as model compounds for styrene polymers. The composition of styrene-a-methylstyrene copolymers was calculated from the ratio of the extinction coefficients of the absorption bands (122).Littke et al. (151)applied a computer analysis to the complex IR peaks at 760 cm-l in the spectra of butadiene-styrene and acrylonitrile-styrene copolymers. Sefton and Merrill (174)discussed the IR spectra of butadiene-styrene block copolymers hydroxylated with peracetic acid. Parrish related (164)the capacity of sulfonated divinylbenzene-styrene copolymers to the amount of styrene produced on pyrolysis and to the absorbance of the IR peak a t 1008 cm-'. Intensity of the absorption peak a t 1200 to 1250 cm-l was used to obtain information concerning the length of the CH&(CH3)R sequences in copolymers of 2-substituted propene and styrene or acrylonitrile (175).The absorption band reached its full intensity a t a length of approximately 5 monomer units. With decreasing sequence length the band intensity decreased and the position of the band shifted to higher wave numbers. Wu and Hsieh (189) determined the composition of acrylonitrile-vinyl acetate copolymers from the IR spectra using the formula (AlIA2 = 19.683 - 0.1986~where A 1 and A2 are the absorbances a t 1725 and 2225 cm-l, respectively, and x is the mole percent of vinyl acetate. IR spectroscopy was used to study styrene oligomers containing acrylonitrile active ends (180). The addition of acrylonitrile to oligostyrene alkylmetal salt solutions resulted in attachment of acrylonitrile across the double bond of the oligostyrene and by formation of the carbanion C-HCN. Mikhailov and co-workers (155) showed that the equation for determining triad distribution in styrene-acrylonitrile copolymers from the intensities of bands a t 1585 and 1603 cm-l is invalid. The sequence distribution of styrene in acrylonitrile-styrene copolymers was calculated by Oi and Moriguchi (162)from the ratio of the C-H out-ofplane bending vibration band at 760 cm-l to the out-of-plane ring deformation band a t 700 cm-l. IR spectroscopic studies by Litovchenko et al. (150) showed that the first reactions occurring in oriented polyacrylonitrile films during heating in air above 145 "C were the formation of conjugated unsaturation in the backbone without loss of CN groups followed by the appearance of carbonyl-containing products. Transitions in polyacrylonitrile, polymethacrylonitrile, and acrylonitrile copolymers were determined by coupling a high resolution spectrometer to a thermal controller (187). IR spectra were obtained during heating and cooling cycles. The amount of grafted polyacrylonitrile chains in acrylonitrile-ethylene copolymers was determined from the ratio of absorptivity at 2246 cm-' (CN stretching vibration) to that a t 4310 cm-1 (CH deformation overtone vibration in polyolefins) (19). Nerheim (158)described a circular calibrated polymethylene wedge for the compensation of CH2 interferences in the ANALYTICAL CHEMISTRY, VOL. 49, NO. 5, APRIL 1977

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determination of methyl groups in polyethylene by IR spectroscopy. Dlugosz and co-workers (120) used Raman spectroscopy, low angle x-ray scattering, and electron microscopy to study the crystal structure of polyethylene, while Willis and Cudby (184) described the use of low-frequency spectroscopy in the far IR region for studying the crystallinity of polymers such as polyethylene, polypropylene, and poly(tetrafluor0ethylene) (PTFE).Dankovics (117 ) determined the degree of branching, the length of the side chains (methyl, ethyl, and butyl branches) and the degree of unsaturation of low density polyethylene. The total degree of unsaturation in polyethylene was determined by summing the vinyl, vinylene, and vinylidene unsaturation derived from the differential IR spectra using an unbrominated polyethylene film as the sample and a brominated film as the reference (171). Popov and Duvanova (167) determined a-olefins in ethylene-olefin copolymers (e.g., 1-butene-ethylene copolymer) by determining the concentration of methyl groups and introducing a correction for the concentration of terminal methyl groups in the main polymer chain. The stretching vibration of the C=O group a t 5.787 km was used to give a quantitative measure of maleate (dibutyl maleate, bis(2-ethylhexyl) maleate) in dialkyl maleate-ethylene copolymers (132). Modric and co-workers (156) observed a distinct change in the wavenumber and the intensity of the absorbance bands between 600 and 500 cm-l with increasing side chain length of poly (1-Cl-20 alkylethylenes). Maier and Brettschneiderova (153) used the 975/1000 cm-l infrared double band to determine the tacticity of polypropylene. Tabb and co-workers (178) used FTIR to study the effect of irradiation on polyethylene. Aldehydic carbonyl and vinyl groups decreased and the ketonic carbonyl and trans-vinylene double bonds increased on irradiation. The crystal structure of polyethylene was determined by Krimm (144), Ching and Krimm (112) and by Fraser et al. (125).Frank and Wulf (124) heated polyethylene above 75 "C and observed that the strong IR absorption peak a t 73 cm-l was displaced to lower frequencies and its intensity decreased. The effect of electrical discharge in the atmosphere on structural changes in polyethylene films was studied by Guseinov and co-workers (129). Ozonides were formed down to a 12-km depth and carbonyl groups down to 4 km. Some low molecular weight compounds containing RON02 groups formed on the film surface. Klein and Briscoe (141) developed a technique for studying the diffusion of large molecules in polymers based on IR microdensitometry. A method for determining the block structure in 1-hexene-4-methyl-1-pentenepolymers from IR spectral data was developed (12). IR bands in the region of CH2 bending and rocking vibrations in the IR spectra of isotactic poly-a-olefins were found to be sensitive to changes in the state of order (133). Matsumoto e t al. (154) showed that the OH groups in partially saponified ethylene-vinyl acetate copolymers had a block distribution, whereas OH groups in partially acetylated ethylene-vinyl alcohol copolymers had a random distribution. Many OH groups in ethylene-vinyl alcohol polymer were hydrogen bonded to neighboring carbonyl groups, whereas the OH groups in ethylene-vinyl acetate copolymer existed mainly as free OH groups. The approximate degree of isotacticity of crystalline poly(3-methyl-1-butene) was determined from the ratio of the absorbance a t 778 cm-l to 1180 cm-l (140). The IR spectra of isotactic poly( 1-pentene),poly (4-methyl-l-pentene), and atactic poly(4-methyl-1-pentene)were reported by Gabbay and Stivala (127). IR and laser-Raman spectral analysis of chlorinated polyethylene indicated that chlorination occurred in the amorphous regions of the polyethylene (148).Quenum et al. (168) studied chlorinated polyethylene over the 19-73% chlorine range. At 73% chlorine content, chlorinated PE and chlorinated PVC had nearly the same spectrum; however, they differed significantly from that of PVDC. Stanciu (176) used infrared analysis to show that the macromolecular orientation of poly(viny1 chloride) was affected by thermal and solvent treatment. Baruya and co-workers confirmed the presence of a spectral band a t 647 cm-l in the spectrum of syndiotactic poly(viny1 chloride) (PVC) by Raman spectroscopy. The band was the result of a coupled vibration of frequencies represented by the bands a t 607 and 637 cm-1. The bands at 1124 and 1511 cm-l in the Raman 164R

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spectra of PVC, after thermal degradation, were shown by Gerard and Maddams (128) to be due to a resonance Raman effect from conjugated polyene sequences. Cais and O'Donnell ( I l l ) followed the dehydrochlorination of sulfur dioxide-vinyl chloride copolymers. The data obtained from IR and UV spectroscopy, proton, and 13C NMR, suggested that hydrogen chloride was eliminated preferentially from chloroethylene units occurring between two sulfonyl units. Coleman and Painter (114) using FTIR separated the IR bands for the preferred conformation of semi-crystalline trans-1,4-polychloroprenefrom the total IR spectrum. A new band was observed near 14 cm-l in the vibrational spectrum of PTFE. Assignment of the band completes the vibrational assignment for the polymer (185). Sintered-PTFE exhibited a band a t 277 cm-l which originated from chains of bent conformation; the fundamental Raman-active IRforbidden bands a t 292 and 312 cm-l were found to originate from chain folds in the crystalline region (186). Perelygin et al. (166) developed an IR spectroscopic method for determination of the degree of crystallinity of PTFE. Jones and coworkers (139) interpreted the strong polarization of the three sharp lines in the 50 cm-l region of the spectrum of P T F E a t liquid nitrogen temperatures in terms of the lattice-mode theory and of possible unit cell symmetries. Davidson and co-workers (118) studied orientation in PTFE using dichroism and broad line nuclear magnetic resonance measurements. Poly(viny1idene fluoride) was shown to exist in three conformations, each of the conformations having its characteristic IR bands (149). The molar ratio of resole-type phenol-formaldehyde resins was determined using the absorbance ratios of D1590 to D2920, D1610, D1150, D1010, and D760 (121). IR spectra showed that the chemical composition of phenol-formaldehyde resin foams was not affected by the method of curing (147). The addition of a toluenesulfonic acid hardener increased the CH20H groups and p-substituted rings. While small changes in the phenol-formaldehyde ratio had little effect on the composition, a significant increase in formaldehyde concentration increased bridge formation and the amounts of ortho and para substitution. The curing of phenolic resins is attended by condensation of methylol groups and formation of ether bridges which then break down as the curing time increases to give rise to methyl groups. (1811. A method for determining the degree of branching in POlyethyleneimine (PEI) was developed by Berezkin et al. (15) based on the IR spectra resulting from the reaction of acrylonitrile with PEL Fountain and Haas (123) found that the presence of water in epoxy resin-dicyandiamide copolymers altered the 2C=N IR absorptions in the 2200 cm-l region, reducing the 2210 cm-' peak more than predicted stoichiometrically. Molecular associations in amine-hardened epoxy oligomers were studied by Noskov (159). The vinyl/phenyl ratio in poly[phenyl(vinyl)siloxanes]was determined by Andrianov et al. (11)based on the intensity ratio of the absorption peaks at 1405 cm-l (CHp=CH) and 1430 cm-1 (phenyl). The method could not be used for analyzing siloxanes containing methyl groups since the methyl absorption peak covered the CH2=CH and phenyl absorption peak areas. The conformation of siloxane rings in cyclolinear poly(phenylsi1sesquioxane) was studied by dichroism of the Si-0-Si absorption bands (182). Krasikova and co-workers (143) developed an IR spectrometric method for the determination of SiOH groups in polysiloxanes. IR and NMR data obtained during the formation of poly(p-diisopropenylbenzene) by Nasirova et al. (157) indicated that polymerization occurred through only one isopropenyl group per monomer. Boerio et al. (16), discussed the band assignments in the Raman spectra of ethylene glycol-terephthalic acid-d* polymer. The composition of cotton-polyester blends was determined from measurements of the polyester C=O stretching a t 1725 cm-l (137). The acrylate salt in acrylate salt-ethylene ionomers was determined by Czaja and co-workers (116) from the ratio of absorbances a t 1560 cm-1 (asymmetric vibration of the carboxylate ion) and 1380 cm-l. The composition of methacryloyl chloride-vinyl acetate copolymers was determined by Bazarbaev et al. (14) from the optical densities of the IR absorption bands a t 1735 cm-l (ester carbonyl) and 1795 cm-l (acid chloride).

Hartley et al. (130),used Raman scattering from the longitudinal acoustic mode in crystalline poly(ethy1ene oxide) to study crystal structure. Results from a,w-hydroxy poly(ethylene oxides) with C1-Cls alkoxy groups indicated that samples with lower and higher alkoxyl groups crystallized in chain-extended and folded forms respectively. The sample with C7 alkoxyl groups formed both types of crystals. The monoconfigurational sequence distribution for poly(propy1ene oxide) was determined from the band shape analysis of the IR spectra within the range of 1240 to 1300 cm-l (145). Vorontsov and co-workers (183) obtained Raman spectra of poly(2-methyl-5-vinylpyridine)and poly(2-methyl-5vinylpyridine hydrochloride) using an argon laser as an excitation source. The spectra consisted of Raman peaks on a fluorescence background. Raman spectra of poly(2-vinylpyridine) and poly(4-vinylpyridine) could not be obtained because of interference of strong fluorescence. Hydrogen bonding in toluene diisocyanate based polyurethanes was studied by Sung and Schneider (177).The amino (NH) groups in all the polymers were hydrogen bonded. In the 2,g-toluene diisocyanate based polymer, 80%of the carbonyl groups were hydrogen bonded to the urethane groups; but in the 2,4-toluene diisocyanate based polymer segment, only 50% of the carbonyl groups were hydrogen bonded. The other proton acceptor was the ether oxygen of the soft segment. Macknight and Yang (152)studied the hydrogen bonding in polyurethane based on 1,6-hexane diisocyanate, 4,4’-diphenylmethylene diisocyanate, and 4-methyl-1,3-phenylene diisocyanate. A correlation between the endothermic activity and hydrogen bonding activity was shown for aromatic urethane-urea segmented copolymers (110). The number ( n )of oxyethylene units in a molecule of oxyethylenated caprolactam was determined from the ratio of the IR bands characteristic of the ether group (1080 cm-l and 1125 cm-l where n is less than 3 and at 1110 cm-l where n varies from 3 to 13) and of the carbonyl of the tertiary amide occurring at 1660 cm-l (163).Earlier conclusions indicating that a t room temperature, over 99% of the N H groups in polyamides were hydrogen bonded have been confirmed by Schroeder and Cooper (173). T h e glycidylmethacrylate content of methyl methacrylate-glycidyl methacrylate copolymers was determined from the ratio of the IR absorbance a t 907 and 1717 cm-l (165). Polarized IR spectra of elongated films of alternating butadiene-methyl methacrylate polymer showed a strong dichroism. No dichroism was observed for random copolymers which showed poor stretching properties (126). Pyrolysis-IR spectroscopy was used by Leukroth (146) to determine the chemical composition of plastics and rubber containing high proportions of pigments or fillers. The temperature dependence of the IR dichroism of cellulose acetate was examined a t 900 cm-l (CH bending) and a t 600 cm-l (acetyl groups). Crandall et al. (115)showed that IR bands a t 1950 and 2300 nm were useful for observing the amidization and imidization processes in the preparatioi of polyamic acids.

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LIQUID AND THIN-LAYER CHROMATOGRAPHY Fallick e t al. ( L 5 ) discussed the use of liquid chromatography (LC) to separate additives and other low molecular weight components from impact polystyrene and polyethylene. Polypropylene was extracted with tetrahydrofuran (THF) for gel permeation chromatography (GPC) and with methylene chloride for LC determination of antioxidants (L23).Simpson (L20) reviewed the use of thin-layer chromatography (TLC) and gas chromatography for the determination of antioxidants, ultraviolet absorbers, and organotin heat and light stabilizers. TLC on silica gel was used by Kazarinova and Novitskaya ( L I 1 )to determine microquantities and 2,6-diisoof 2,6-bis(a-methylbenzyl)-4-methylphenol bornyl-4-methylphenol used as heat and light stabilizers in polymeric materials. Kamiyama and Inagaka (L14) studied the effect of single and binary solvents of increasing dielectric constants on the TLC separation of polymers on silica gel. Gankina and coworkers ( L 6 ) discussed the feasibility of separation of oligomers according to molecular weight by TLC based on the difference in absorption activity of the terminal and central

units in the macromolecules. Illustrations were provided for the separation of oligomeric polystyrene and poly(a-methylstyrene) without terminal functional groups, poly(oxyethylene) with active terminal and central units, and poly(dimethylsiloxane) containing inactive central units and esterified with 3,5-dinitrobenzoic acid for blocking the active terminal groups. Random, tapered, diblock, and triblock butadiene-styrene copolymers were separated by TLC ( L 4 ) . Gloeckner and Kahle ( L 8 ) separated acrylonitrile-styrene (SAN) copolymers into fractions differing in acrylonitrile content by a temperature gradient TLC on silica gel using a toluene-acetone mixture as the eluent. SAN copolymers were fractionated by Gloeckner and Kahle (L7) by TLC on silica gel D using a benzene or toluene solvent to which acetone was gradually added. T h e developing solvent must dissolve the polymer and must also be polar enough to displace the polymer in the resorption layer. The compositional heterogeneity of styrene-methyl methacrylate block copolymers was determined by TLC and compared with the results obtained from cross-fractionation and a computer simulation method (L13). The compositional distributions agreed in all three methods and were found to be unexpectedly broad. A combination of GPC followed by TLC of the fractions followed by pyrolysis-gas chromatography (PGC) of the TLC fractions was used to study the polydispersity of block copolymers of styrene and methyl methacrylate; PGC yielded quantitative data on the polymer composition of fractions previously separated by GPC on the basis of size and by TLC on the basis of composition (L2).Horii and co-workers (L10)applied TLC to study the purity of graft copolymers. Homopolymers were easily detected in styrene-vinyl alcohol graft copolymers after acetylation of the mixture. Valuev et al. (L22)separated oligomeric butadiene-isoprene block copolymers into fractions containing 2,l and no terminal hydroxyl (OH) groups, respectively, by TLC. Infrared spectroscopy was used for the determination of OH content. Miyamoto and co-workers (L16) separated isotactic poly(methyl methacrylate) from syndiotactic poly(methy1 methacrylate) using competitive absorption on silica gel from chloroform. Cyclic oligomers in poly(ethy1ene terephthalate) were determined by TLC using chloroform-ether (9:l) as a solvent (L17). Belen’kii et al. ( L 3 ) determined the number of OH groups in poly(propylene oxide) and OH-containing impurities such as alcohol by TLC on silica gel. Water-saturated ethyl acetate with 2% methyl ethyl ketone was used as the eluent. Polyamides, polyurethanes, and polyimides were distinguished by TLC of the HCl hydrolysis products (L9).Free toluene diisocyanate and 4,4’-diphenylmethane diisocyanate were determined in polyurethane prepolymers by McFadyen (L15)using high performance LC with dioxane as the solvent. OH group-containing oligoethers and oligoesters used in polyurethane preparation were separated by TLC on thick silica gel. Polyethers were developed with ethyl acetate containing varying amounts of methyl ethyl ketone while the polyesters were developed with benzene or T H F containing ethanol (L21).Klacel and Svoboda ( L I Z )separated diamine and diol fractions of polyester-urethane hydrolyzates by TLC and GC. Dicarboxylic acids were determined using a temperature gradient TLC technique. Unreacted 4,4’-methylenebis(o-chloroanaline) (MOCA) was determined by Becker and co-workers ( L 1 ) during vulcanization and in urethane rubber vulcanizates by quenching the sample in T H F saturated with ammonia and determining the MOCA by LC. High-performance LC was employed to determine the components of phenol-formaldehyde copolymer condensation products ( L I 8 ) .A method was developed for determining the molecular weight distribution of phenol-formaldehyde co, paper chromatography polymers by Siling et al. ( L I 9 ) using with acetone-light petroleum ether as the eluent.

MASS SPECTROMETRY Hummel et al. ( M 3 ) reviewed the application of mass spectrometry (MS) to the analysis of polymers. Sigmond (M7) determined the volatile content of plastics and rubber samples by outgassing a t various temperatures in the unmodified ion source of a high resolution mass spectrometer; the sensitivity of the spectrometer was monitored by a constant influx of argon gas. ANALYTICAL CHEMISTRY, VOL. 49, NO. 5, APRIL 1977

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The fragmentation mechanism and the composition of polystyrene oligomers were determined by Beckewitz and Heusinger ( M 1 ) .Yamamoto et al. ( M 8 ) ,reported mass spectra for a-methyl styrene dimer, trimer, and other oligomers prepared in living systems. Futrell and co-workers ( M 2 ) developed an integrated analytical system providing simultaneously gas chromatograph (GC) retention time, electron impact, and chemical ionization MS to evaluate the combustion and thermolytic degradation products of polymeric materials. Montaudo and co-workers ( M 5 ) established the thermodegradation mechanisms for poly(oxy-1,4-phenylene),POly(thio- 1,4-phenylene), and poly(dithio- 1,4-phenylene) by direct pyrolysis of the polymers in the ion source of a mass spectrometer. The electron impact induced fragmentation of the pyrolytic fragments was suppressed by using low ionization energy. The component monomers of polyurethane foams were identified by Reed ( M 6 )by heating the foam and identifying the evolved gases by time-of-flight MS. Mol et a1 (M4), discussed MS applications in thermal analysis of polymers. Direct identification of thermolysis/pyrolysis fractions was accomplished by attachment of a rapid scan spectrometer to the exit port of a GC. The mass spectrometer itself provided a thermolysis method for polymer analysis by use of a direct insertion probe with controlled heating or by heating a portion of a glass inlet system of the mass spectrometer in a controlled manner to volatilize the products into the ion source of the mass spectrometer.

NUCLEAR MAGNETIC RESONANCE A number of reviews on the application of nuclear magnetic resonance (NMR) to the analysis of synthetic high polymers were published during the past two years. Schaefer (N91) reviewed the use of 13CNMR for determining the steric configuration in homopolymers and sequence distribution in copolymers. Katritzky and Weiss (N51)described the use of 13C NMR to define the tacticity of polymers and copolymers and the monomer sequence structure of copolymers. General reviews were published by Schaefer (N92),Plate and Stroganov (N80),Robb and Tiddy (N86), Klesper and Sielaff ( N 6 0 ) ,and Folkes and Ward (N35).Blouin ( N 5 ) discussed the application of 300 MHz proton NMR to the characterization of alternating copolymer systems. The use of Carbon-13 Fourier transformed NMR and proton enhanced Carbon-13 NMR in polymer characterization was described by Moniz et al. (N72). The amorphous component of carbon disulfide-wetted poly(4-methyl-1-pentene) and trans-1,4-polybutadiene was studied by broad-line NMR (N30, N31). Pulsed Fourier transformed 13C NMR was used by Carman (N14) to show that butadiene-propene polymers prepared with V or T i catalysts had perfectly alternating monomer sequence distribution. 13C NMR data were shown to be more sensitive to structure modifications than PMR. Yamashita and co-workers (N112) used high-resolution NMR to show that styrene-isobutene and a-methylvinyl methyl ether-methyl vinyl ether copolymers had a random structure. The degree of branching of poly(viny1 chloride) (PVC) and of polyethylene (PE) was determined by Bezdadea et al. (N4). 13C NMR studies by Elgert et al. showed that polybutadiene (PB) prepared using butyllithium in tetrahydrofuran a t -10 "C contained approximately 80% 1 , 2 units and was predominately syndiotactic. Shift assignments obtained from 13C NMR spectra of model compounds such as cis,trans-4,8dodecadiene-l,12-dial were used by Deneke and Broecker (N21) to determine the microstructure of PB. The microstructure of poly-trans -1,3-pentadiene prepared in heptane a t 80 "C with butyllithium catalyst was found by NMR spectroscopy a t 90.51 MHz to contain 15% 1,2 and 85% 1,4 units; 30% of the 1,4 units were cis and 70% were of trans configuration (N28).The 13C NMR spectra of PB were interpreted and signals assigned to cis-1,4, trans-1,4 units and 1,2 units by Elgert et al. (N26,N27).Hatada et al. (N45)used spin decoupling techniques in NMR spectroscopy to show that the distribution of cis and trans units in PB was statistically random. Lindsay et al. (N64,N65) prepared 300 MHz NMR 166R

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spectra of highly alternating and conventional butadieneacrylonitrile copolymers. In the alternating copolymers, the olefinic proton resonance of acrylonitrile was observed as two patterns of equal intensity assigned to protons in the meso and racemic acrylonitrile-butadiene-acrylonitrile triads. The resonance of acrylonitrile methine and methylene protons was observed as four patterns of approximately equal intensity. The methine proton resonance of the free radical-initiated acrylonitrile (A)-butadiene (B) polymer was observed in three areas and was used to measure the relative amounts of AAA, AAB, and BAB triads. The probabilities of occurrence of various compositional configurational triads in methacrylic acid-methyl methacrylate copolymers were studied by Klesper et al. (N59)using both proton and 13C NMR. Spevacek and Schneider used high-resolution NMR (N100, N101) and broadline NMR (N102)to study the structure of the stereocomplex of isotactic and syndiotactic poly(methy1 methacrylate) (PMMA). Schaefer and co-workers (N93) determined the individual spin-lattice, nuclear Overhauser, and rotating-frame crossrelaxation parameters for individual carbon atoms in solid PMMA using natural abundance, dipolar-decoupled l3C NMR. The dipolar-decoupled NMR spectra of polystyrene was improved sufficiently by magic-angle spinning a t 2 kHz to permit determination of relaxation parameters. Sequence distribution and stereoregularity in radical and anionic-initiated methyl acrylate-methyl methacrylate copolymers were calculated from proton NMR spectra (N73).220-MHz NMR spectra of alternating methyl methacrylate-butadiene and methyl methacrylate-isoprene copolymers indicated an isotactic configuration with flanking butadiene units (N106). Ebdon (N23)related the intensities of the various a-methyl signals in the 220 MHz PMR spectra of free radical polymerized chloroprene-methyl methacrylate copolymer to the relative proportions of the various methyl methacrylate centered triads. Roth and co-workers (N87)compared the 13C NMR chemical shifts of ethylene-methyl acrylate polymer and ethylene-ethyl acrylate polymer with the shifts calculated from electron density by the extended Nueckel molecular orbital theory. McGrath and Robeson (N69) used 100-MHz NMR spectroscopy to characterize ethylene-ethyl acrylate copolymers, ethylene-ethyl acrylate-carbon monoxide terpolymers, and ethylene-2-ethylhexyl acrylate-carbon monoxide terpolymers. Assignments and quantitative analyses for all tetrad peaks in the backbone CH2 resonance of poly(methy1-a-chloroacrylate) were made from 300-MHz NMR spectra (N22).Clay and Charlesby (N17)postulated that the triplet in the electron spin resonant spectrum of poly(acry1ic acid) polymerized by gamma irradiation actually consisted of a doublet or triplet and a singlet. Heublein and co-workers (N46)determined the concentration of diads and mean sequence lengths in copolymers of methyl-a-chloroacrylate-methyl methacrylate and methyl methacrylate-trimethylsilyl methacrylate copolymers from 13C NMR spectra. Keller and Roth (N57)used 13C NMR to determine the sequence distribution in ethylene-methyl acrylate copolymers. Sobottka and co-workers (N95) described a method for determining activation temperatures of various kinds of molecular motion and degrees of order in crystalline polymers such as P E using broad line NMR. Keller and Muegge (N55) calculated chemical shifts for ethylene-vinyl chloride copolymers, ethylene-vinylidene chloride copolymers, and chlorinated PE from measurements of hydrogen broad band-decoupled 13C NMR spectra. Cudby and Bunn (N20) used eicosane as the standard for determining the optimum conditions for relative intensity measurements of ethyl, butyl, and longer chain branches in low density polyethylene. T h e average number of branch points per 1000 carbon atoms for ethylene-propylene copolymers, 1-butene-ethylene copolymers, ethylene-1-hexene copolymers, and low density polyethylene was calculated from the I3C NMR spectra. The branches of low density P E were shown to consist of butyl groups (N43). Ahmad and Charlesby ( N 2 ) used broad line NMR to study the effect of branching and structural changes on the glass transition temperature and activation energy of molecular motion of high and low density PE and ethyleneacrylic acid block copolymers. Broad line NMR spectra of drawn high density P E showed three component lines: a broad component assigned to crys-

talline regions; an intermediate component assigned to high molecular weight molecules interconnecting the crystalline regions; and an isotropic narrow component assigned to mobile low molecular weight material and the ends of molecules rejected from the crystalline regions (N98).Wu and Ovenall ( N I I I )utilized 220 MHz proton and 22.6 MHz 13C NMR to characterize the comonomer sequencing of ethylene-carbon monoxide copolymers. Keller and co-workers (N52)calculated the composition of 2-chloroethyl acrylate-ethylene copolymers from the 100-MHz undecoupled proton resonance spectra. The same authors utilized high resolution NMR spectroscopy to determine the side chain content and sequence distribution of ethylene-glycidyl acrylate copolymers (N53). Stehling and Knox (N103) defined the stereochemical structure of PP from the PMR spectra of normal, deuterated, and epimerized PP. Mitani (N71) found that the diad and triad content of isotactic PP, syndiotactic PP, and atactic PP, as determined from 100-MHz NMR spectra, were in agreement with the values determined from the 220-MHz NMR and I3C NMR spectra. Radtsig (N82) studied the structure and conformation of free radicals formed during the radiolysis and mechanical degradation of isotactic PP and poly-1-butene. Analysis of the 300-MHz proton NMR spectra of poly(4methyl-1-hexane) by Kennedy and Johnston ( N 5 8 )showed that the molecular structure was not that of a completely isomerized 1,4 structure. These findings are in contrast to those for poly(3-methyl-1-butene) which has a completely isomerized structure, and to those of poly(4-methyl-1-pentene) which can be modified by changing the polymerization temperature. Brame and co-workers ( N I 0 )used proton and 19FNMR spectroscopy to determine the triad sequence distribution of propylene-tetrafluoroethylene polymers. Brame ( N 9 ) reviewed the 19FNMR of fluorocarbon polymers. The structure and composition of copolymers of vinylidene fluoride with perfluoroalkyltrifluoroethers was determined by Sass et al. (N89)using 19FNMR at a frequency of 84.67 MHz. Vinylidene fluoride block units were identified through the signals for the CF2 groups. Based on 19FNMR and 13C NMR spectra, Toy and Stringham (N109)concluded that the microstructure of polyperfluorobutadiene consisted mainly of 1,4 moieties. Based on the infrared spectrum, the infrared inactive trans1,4 moiety was suggested as the predominant configuration. Bovey and co-workers ( N 8 )demonstrated that the branch structure of PVC was -CH2CHClC(CH2Cl)HCH2CHCl- by 13C NMR after reduction of the polymer with LiA1D4. The differential enthalpy and entropy changes for bulk PVC were estimated from triad tacticity data obtained from the pentad measurement ( N I ) .Repko and co-workers (N84)used wideband NMR to determine the crystallinity of PVC and poly(vinylidene chloride). The crystallinity for PVC agreed well with that determined by x-ray analysis. The crystallinity of poly(viny1idene chloride) calculated from NMR data was not in agreement with that determined by x-ray analysis. Keller et al. (N56),determined the structure and the number of CH2, CHC1, and CClz groups in chlorinated PVC using proton and 13C high-resolution NMR. Cais and O'Donnell (N13)analyzed the 13C proton NMR spectra of sulfur dioxide-vinyl chloride copolymers in terms of comonomer sequences and configurational placements. Wu and Ovenall (NIIO)used proton NMR to determine the tacticity of acetylated poly(viny1 alcohol) (PVA) and noisedecoupled Fourier transformed 13C NMR to determine triad, tetrad, and pentad sequences. Noise-decoupled pulsed Fourier transformed 13C NMR spectroscopy was used by Ibrahim et al. (N48)to study tacticity in poly(viny1acetate) and monomer sequence distribution in ethylene-vinyl acetate copolymers. Broad-line NMR spectroscopy was employed by Sobottka et al. ( N 9 9 ) ,to show that methyl group rotation in ethylenevinyl acetate copolymers occurred a t temperatures below -196 "C. Keller (N52) determined the monomer sequence distribution in ethylene-vinyl acetate polymers from the methine and methylene carbon regions of 13CFourier transformed NMR spectra using proton broad-line coupling. Short-chain branching in PVA was determined by Morishima et al. (N74, N 7 5 ) ,from NMR spectra. The short branches in PVA were found to be equal to or greater than two monomer

units in length and are formed by a back-biting mechanism. Based on a comparison of the 13C NMR spectra of polystyrene and of deuterated polystyrene, Ebdon and Huckerby ( N 2 4 )assign the high field peak a t 6 40.5 ppm to the aliphatic methine (CH) group. Laupretre et al. (N62)identified the configuration isomers of 2,4,6&tetraphenylnonane from the 13C NMR spectra using the results obtained for model compounds such as 2,4-diphenylpentane and 2,4,6-triphenylheptane. From broad-line NMR spectra, Morita and Shen (N76) concluded that plasma polymerized styrene has a mesh-like cross-linked network structure in which low molecular moieties are trapped and which can be removed by heat in open air. A random distribution of styrene monomer units in styrene-maleic anhydride copolymers was indicated by the NMR chemical shifts of four triads in 1:3,1:2, and 1:l maleic anhydride-styrene copolymers ( N I I ) . The microstructure of styrene-methyl methacrylate copolymers was studied by Brockrath and Harwood ( N 7 ) ,by Stroganov and co-workers (NI04),and by Blouin et al. ( N 6 )using PMR and by Kat0 et al. (N49) and by Katritzky e t al. (N50)using 13C NMR. Diad, triad, and pentad configurational distributions were evaluated from the NMR spectra. Katritzky et al. found that the aromatic C-1 in styrene and the methyl carbon in methyl methacrylate units of the copolymer were sensitive to tacticity in monomer sequence triads. The various proton resonances in the NMR spectra of poly(p -isopropyl-a-methylstyrene)were assigned by Leonard and Malhotra ( N 6 3 ) ,to isotactic, heterotactic, and syndiotactic triads. Regel and co-workers (N83)used 19FNMR and PMR to study the syndiotactic and heterotactic triads in poly(p-fluoro-a-methylstyrene) copolymers. The triad distribution determined by 19FNMR agreed with the distributions determined from PMR of the a-methyl protons even though the fluorine nucleus was relatively far removed from the main chain. Sandner et al. ( N 8 8 ) ,calculated the diad and triad distribution in acrylonitrile-styrene copolymers from the resonance of the quaternary carbon of the phenyl groups in the styrene units, the CN group of the acrylonitrile units, and the CH2 groups in the main chain from 13C NMR spectra. Carbon-13 NMR spectrum of alternating copolymers of a-methyl styrene and methacrylonitrile were shown to be dominantly syndiotactic in contrast to PMR results (N29). Gronski et al. (N40) showed the segmental motion in butadiene-styrene copolymers to be influenced by sequence distribution as determined by 13Cspin lattice relaxation times. The relaxation times for 1,4-diene units at boundaries with styrene or 1,2 units are different from those in block sequences; the relaxation of the o-phenyl carbon atoms is slower than p-phenyl relaxations. Chokki and co-workers ( N I 6 )employed NMR spectra of phenylcarbamoyl derivatives of polyether polyoles and polyester polyoles to determine the OH end-group content. Proton and 13CNMR spectra were employed by Fleischer and Schulz (N32-N34) to analyze the sequence distributions in poly(ethy1ene oxide), poly( 1,3-dioxolane), poly( 1,3,5-trioxepane), poly(l,3,6-trioxocane),and 1,3-dioxolane-1,3,5-trioxane copolymers. The chain structure of trioxane-1,3-dioxolane copolymers was also studied by Bulai et al. (NIL?),and by Opitz ( N 7 9 ) ,using 13C NMR and proton NMR, respectively. The structure of bisphenol-A diglycidyl ether-piperidine polymer was defined by Sojka and Moniz (N96) using Carbon-13 NMR. Phase separat,ion in binary polymer systems was studied by Nagumanova et al. ( N 7 7 ) ,using broad-line NMR. A non-additive increase in the second moment (M2) of the NMR line was observed in the region of critical concentration of the second polymer. For polycarbonates, the non-additive changes in Mz were explained by an increase in the degree of ordering of the polycarbonate upon transition from a single phase to a two-phase system. The composition of mixed polycarbonates formed by the polycondensation of bisphenol with phosgene and 5-azidoisophthaloyl chloride was determined by Smirnova et al. (N97). Slonim et al. (N94)used Carbon-13 NMR to determine the molecular weight distribution of polymethylene glycol, in aqueous formaldehyde solutions, from the equilibrium constants of formaldehyde hydration. Alekseeva et al. ( N 3 )used the signals of the aromatic protons in the NMR spectra of

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formaldehyde-resorcinol polymers to determine the isomeric composition. Richard and Gourdenne (N85) used NMR analysis to show that, in the cross-linking of formaldehydeurea polymers, methylol groups condensed to form ether bridges with elimination of water. No methylene bridges were formed, and NH2 and N H roups remained unchanged. Chiavarini et al. (N15) used model compounds such as monomethylolurea to interpret the NMR spectra of formaldehyde-urea copolymers. The content of free methylol, methylene, oxymethylene formaldehyde, and nonsubstituted mono-, and disubstituted amide groups were determined from the NMR spectra of the copolymers in dimethyl sulfoxide-d6 solution. Triad, tetrad, and pentad tacticities in polymethacrylonitrile were determined by Matsuzaki et al. (N68) using 13C NMR. Oligomeric polyurethanes prepared from secondary diamines, diisocyanates, and glycols were employed by Martin and Gourdenne (N66) as model compounds for 90-MHz proton NMR analysis. Toppet and co-workers (N108)found that the 13C spectrum of poly-4-vinyltriazole in dimethyl sulfoxide exhibited the presence of three sets of 2 aromatic carbons. O'Neill and Pringuer (N78) used 13C Fourier transform NMR to analyze mixtures of 2,4- and 2,6-toluene diisocyanates, whereas Platten ( N 8 I )used PMR for the same analysis. The methyl proton resonances for the 2,4 and 2,6 isomers were separated when C6F6 was used as the solvent. Kricheldorf et al. (N61),compared the 13C NMR spectra of alternating polyamides with block copolymers. The 13C carbonyl signals of the monomer units in alternating polyamides showed a larger shift from each other than in the corresponding block copolymer. Matsuzaki e t al. (N67)showed that radical pol merized poly(2-vinylpyridine) was completely atactic by C NMR. Since the absorptions of methine protons overlap in the proton NMR spectra, only isotactic intensities could be obtained. The conformation and rigidity of poly(4-vinylpyridine) chains were determined by Ghesquiere et al. (N37),as a function of the degree of quaternization with HBr and octylbromide at 25 MHz for 13C and at 100 and 250 MHz for proton NMR. Golub and co-workers (N38)applied proton and 13C NMR and infrared analysis to the study of the thermal oxidation of polyisoprene. The ma'or spectral changes were associated with a loss of the original &(CHs)=CH double bonds and cyclization via the ROz radicals accompanied by appearance of epoxy, peroxy, and hydroperoxy groups. Gronski and coworkers (N40) used the chemical shift correction parameters for linear alkanes in the aliphatic region of 13CNMR spectra to determine the relative amounts of 3,4 and cis-1,4 units of polyisoprene. Tanaka and co-workers (N107) showed from NMR spectra that hydrogenated polyisoprene contained 1,4 and 3,4 units randomly distributed. Hummel and Bestgen (N47)studied the composition and configuration of isobutene-maleic anhydride copolymers utilizing proton resonance measurements. Merle-Aubry and co-workers (N70) used the area of the peaks of the nonequivalent proton of CH2 groups to determine the percentage of isotactic diads in poly(methy1 vinyl ketone) and poly(pheny1 vinyl ketone). Nuclear spin relaxation and molecular motions in sebacate polyesters were studied by Froix and Goedde (N36).Relaxations associated with local motion of the methylene units of the chain backbone and with the glass transition and melting transition were observed. High resolution NMR (N90) was used for the qualitative and quantitative analysis of binary polyesters from phthalic and maleic anhydride and ethylene glycol, diethylene glycol, propylene glycol, and dipropylene glycol. The NMR spectra of cyclic tetramers obtained as byproducts in BF3 initiated polymerization of epichlorohydrin or glycidyl nitrate showed the presence of methyl groups (N39). Formation of the methyl groups was ascribed to a hydride shift in the carbanion-ion-terminated growing chain rather than isomerization of the epoxy group to the corresponding aldehyde. Peaks in the 13C NMR spectra of ethylene sulfidepropylene sulfide copolymer were assigned in terms of diad and triad sequences and of tacticity (N19). Guerin and coworkers (N42) used I3C NMR and PMR to measure the stereoregularity of propylene sulfide polymers. 13C NMR spectra of ethylene sulfide-isobutylene sulfide copolymers

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and isobutylene sulfide-propylene sulfide copolymers were obtained by Corno and Roggero ( N I 8 ) .The effects of monoor dimethyl substitution in the a , p, y,or 6 positions on the chemical shifts of the main chain carbon atoms are discussed. Harris and Kimber (N44),studied end- roups and tacticity effects in polymeric silicones employing fgsi NMR.

LUMINESCENCE, FLUORESCENCE, AND ULTRAVIOLET Brestkin and co-workers (P2)reported a method for measuring the polarization luminescence intensity of polymers which could be used for the determination of chain segment orientation. Vrancken (P13)reviewed diffusion measurements by Rayleigh line-broadening spectroscopy. Somersall and Guillet (PIO) reviewed photoluminescence spectroscopy as related to the characterization of synthetic polymers. Allen et al. ( P I ) recorded the fluorescence emission and phosphorescence emission spectra of 19 commercial polymers in the range of 300-450 nm and 400-600 nm, respectively. Patterson (P9)studied the Brillouin scattering of poly(methy1 methacrylate) and polystyrene as a function of temperature. Equilibrium values of Brillouin splitting were observed a t approximately 20 "C below T,. The polarization of the phosphorescence of styrene-vinylbenzophenone copolymers and of the fluorescence of methyl methacrylate-styrene copolymers and methyl acrylate-styrene copolymers is discussed by David et al. (P5)in terms of copolymer composition, low molecular weight compounds, and chain conformation. Brunn and co-workers (P3) determined the amount of free acrylic acid in poly(acry1ic acid) and of ethyl acrylate in poly(ethy1 acrylate) by UV measurements at 195 nm where the extinction coefficients of polymer and monomer differed most. The fluorescence spectra of polyesters with a terephthalate main chain and a pendent w-carbazylbutyl group were explained on the basis of inter- and intramolecular interactions (PII). A computer method of ultraviolet spectrum matching was developed by Daniels and Rees ( P 4 ) to determine the concentration of individual polyenes from the broad absorption spectra of degraded poly(viny1 chloride). Up to six conjugated double bonds, the average wavelength increment for the longest wavelength was approximately 30 nm for each additional double bond. Wynne and Wendlandt ( P 1 4 ) obtained differential scanning calorimetry and light emission curves in nitrogen, oxygen, and air over a temperature range for polyacrylonitrile. In all atmospheres the initial light emission was of the oxyluminescence type associated with hydroperoxide radical formation. Velocity and attenuation coefficient of longitudinal hypersound measurements of poly(propy1ene glycol) by Huang and Wang (P7)showed the presence of molecular relaxations between 250 and 390 K. The observation of entire relaxation in the sound attenuation vs. temperature curve appears to be the first of its kind ever to have been made by Brillouin scattering measurements. Polyurethanes from tolylene diisocyanate, poly(oxypropy1ene glycol) and castor oil were irradiated with x-rays and with UV radiation and the resulting thermoluminescent peaks on a temperature scale showed a correlation with the thawing-out motion of CH3 and CH2 groups (P8). NEUTRON SCATTERING METHODS The application of neutron scattering for determining the size of macromolecules in the glassy state, radius of gyration, the effect of orientation and stretching on dimensions, and conformation of copolymers was reviewed by Allen ( S I )and Benoit (82). Thorpe ( S 5 )found that the antiferromagnetic susceptibility in simple magnetic polymers is nonordering and therefore finite and insensitive to the length of the chain. The random coil configuration and the radius of gyration of polystyrene and polyethylene, employin hydrogen and deuterium-tagged polymers, was determinedeby Schelten and co-workers (S4). Berghmans and co-workers (5'3) studied low frequency

motions in poly(ethy1ene terephthalate) using neutron inelastic scattering. MICROSCOPY Various microscopic techniques were used to characterize the microstructure of cellular silicone (T8),poly-w-undecanamide (2'77, and surfaces of fluoropolymers (2'13). A combination of low an le x ray diffraction and electron microscopy (EM) was usecfto study the structural types in bulk and in concentrated solutions of block copolymers. It was observed that five crystal types: central cubic, hexagonal lamellar, inverted hexagonal, and inverted centered cubic appeared successively as the concentration of insoluble block was increased (2'6). A staining technique, developed for microscopy of butadiene-methyl methacrylate-styrene copolymers, provided a method for following the stages of preparing impact prepolymer and phase inversion (T14). The three-dimensional shape of the domains of an isoprene-styrene-2-vinylpyridine terpolymer was investigated with selective staining of isoprene by osmium tetraoxide and 2-vinyl pyridine by silver nitrate. The terpolymer consisted of an array of roughly spherical particles of mixtures of polystyrene and poly(2-vinyl pyridine) blocks embedded in a polyisoprene matrix (T12). A particle-like morphology was observed in the brittle fracture surface of polystyrene. Its presence is probably an inherent feature of the brittle fracture surface of an amorphous polymer caused bv- plastic deformation at the moment of fracture ( T I1. Methods to determine the molecular structure and particle size of rubber in imDact Dolvstvrene and acrvlonitrile-butadiene-styrene copoiymer u&g phase contrast and E M were described (T16). Lexan (bisphenol-A polycarbonate) was analyzed using EM and small angle x-ray scattering methods. The data represented the bulk material as being characteristic of homogeneous random fluids (2'15). The structure of oriented polyethylene (PE) after high pressure annealing was studied using electron diffraction and EM(T2, T3). Contrast agents such as chlorosulfonic acid with uranium dioxide or uranyl acetate were used to study microstructure of P E (TIO, 2'11). E M was used to observe the ordered nuclei in high density P E on injection molding ( T 9 ) . Chu characterized the morphology of spherulite films of poly(ethy1ene terephthalate) and poly(tetramethy1ene terephthalate) using scanning EM, polarizing optical microscopy and small angle light scattering methods (T4, T5). MOLECULAR WEIGHT (MW) AND RELATED MEASUREMENTS Slade edited two books on "Polymer Molecular Weights" (W28). Batzer ( W 4 ) and Kamide (W16, W17) published reviews of methods for determining the molecular weight (MW) of polymers. Narrow MW distribution (MWD) standards of polypropylene are available from National Physics Laboratories of Teddington, England (W1). Equations, derived to determine MW of backbones in graft polymers, were used to examine acrylic acid-nylon-6 graft copolymers prepared by irradiation of mixtures of the nylon and the acid ( W11). An equation to calculate weight average MW ( g w ) of polymers was proposed emnloying the refraction increment and number average MW (Mn) of a polymer in two different solvents (W27). Ultracentrifugation. Preparative ultracentrifugation was used to study the influence of mercaptan, temperature, monomer flow rate, polybutadiene, initiator systems, and emulsifier on the grafting parameters of acrylonitrile-butadiene-styrene copolymer ( W10). MWD of poly(m-phenyleneisophthalamide) was determined from one sedimentation pattern (W24).The MWD and branching of polyethylene were measured by rapid sedimentation and viscometry (W25). A new method and general

equations to determine MWD of polymers by rapid sedimentation were described (W15). Osmometry. A vapor pressure osmometer was modified enabling measurement of temperature difference -6 X loT6 "C. A method for calculating the Mn using the calibration parameter was described ( W17). Ayrey established the relationship of g n and viscosity of unfractionated low conversion poly(p-chlorostyrene) and poly(o-methoxystyrene) ( W 2 ) . The heterogeneity of olycaprolactam prepared by v a r i a s m e t b d s was determineland compared by measuring the Mn and Mw (W6). Viscosity. Specific and reduced viscosities of polypro ylene (PP) were used to calculate the intrinsic viscosity (77 by a one-point method using the Huggins, Martin, and SolomonCi&a equations. The (7) values were used for the calculation of Mn of polypropylene (W31). Goel determined K,a values in the Mark-Houwink equation of ethyl acrylate-maleic anhydride-styrene polymers in 1,4-dioxane (W13).The de ree of branching of commercial samples of poly(viny1 chlorife) was investi ated with intrinsic viscosity in a 6 solvent mixture of 61.5 vo ume % cyclohexanone and 38.5 volume % 1-butanol at 25 "C (W21). A correction scheme of intrinsic viscosity for polymer solutions provided linear dependence in the Huggins formula and gave accuracy of 0.01 g/dL which was not possible to obtain using single extrapolation calculations (W14). Light Scattering (LS)-Viscosity. Kratochvil reviewed the potentials of the LS method and of some related aspects for the investigation of dilute polymer solutions, multicomponent with respect to both solvents and polymers (W19).He also suggested the useof acetophenone-cyclohexane-ethanol mixed solvent for the Mw determination of butadiene-styrene polymers by LS (W20).A computer program in FORTRAN Iv language was written for a numerical variant of the gra hical Zimm method for interpretation of LS experimenta data ( W26). A LS photometer operating with a He-Ne laser at 1086 nm was described. Precise determination of MW and radii of gyration of larger molecules were obtained. Measurements on synthetic and biopolymers with MW up to 40 X 106 and coil diameter of >IO4 A were used to demonstrate the advantage and limitations of LS in the near infrared ( W 7 ) . LS and viscosity were used to characterize the long chain branching of polyethylene in a-chloronaphthalene a t 127 O (W9). Accurate MW of polystyrene was determined by LS measurements in a mixed solvent of benzene-cyclohexane and benzene-isopropanol which was a B solvent (W29). LS and viscosimetric data of high MW fractions of poly(dibutyl itaconate) indicated a high degree of branching. The rigidity of the chain of the polymer calculated from unperturbed dimensions approached that of cellulose derivatives (W5). The composition heterogeneities of random methyl methacrylate-styrene copolymer ( W 3 )and acrylonitrile-a-methylstyrene (W22) were determined from LS and osmotic pressure measurements in various solvents. Apparent MW of the copolymers in all solvents agreed with each other. Turbidimetric Titration. Turbidimetric titration to determine the MW of polymers was demonstrated with poly(vinyl chloride) ( W S ) ,polystyrene (W18),and poly(ethy1ene oxide) (W15).

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X-RAY M E T H O D S Small-angle neutron scattering and small-angle x-ray scattering techniques for the determination of structure of amorphous polymers were surveyed by Ruland ( X 2 6 ) .Cella and Hughes ( X 6 , X 7 ) reviewed the problems encountered in the use of wide-angle x-ray diffraction techniques for structural analysis of crystalline polymers. Atkins ( X 2 )reviewed the theories of x-ray diffraction and the application of the method to the determination of the molecular and crystal structure of polymers. Schelten and Schmatz (X29) discussed the use of diffraction of x-rays and neutrons in the study of polymers. The determination of polymeric structures by x-ray diffraction methods was reviewed by Bunn ( X 5 ) .The determination of orientation functions and structural parameters ANALYTICAL CHEMISTRY, VOL. 49, NO. 5, APRIL 1977

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of amorphous polymer by x-ray analysis was reviewed by May and Walther ( X 1 9 ) . A numerical desmearing technique was described by Loveall and Windle ( X 1 5 ) to improve wide-angle x-ray diffraction patterns of aligned atactic polystyrene and quenched isotactic polystyrene. Hamada et al. ( X 1 2 ) calculated the molecular weight, radius of gyration, second virial coefficient, mass per unit length, hydrodynamic length, radius of gyration of cross-section for polystyrene in methyl ethyl ketone from measurements of small-angle x-ray scattering. The density of crystalline and amorphous phases in polymers in the liquid and solid states was calculated from x-ray interferometric data by Martirosyan et al. ( X I 7 ) .The density of isotactic polystyrene a t 22 f 0.3 "C was 1.0805 f 0.0005 g/cm3. The structural parameters of styrene-butadiene block copolymers in heptane were determined using small-angle x-ray scattering (X24). The amorphous phases of poly(methy1 methacrylate), polycarbonate, polystyrene, and polyethylene were examined ( X I O ) employing a combination of electron diffraction (determination of short-range order), light and x-ray scattering (mofphology) and neutron small-angle scattering (conformation). Long-range ordering in poly(p-biphenyl acrylate) was studied by Newman et al. ( X 2 2 ) ,employing x-ray difdescribed methodology fraction techniques. Gouinlock (X11) and apparatus for the determination of degrees of order in highly crystalline poly(viny1 chloride) by wide-angle x-ray diffraction. Small-angle x-ray scattering of poly(viny1 chloride) was inter reted in terms of a two-phase system containing orderef and disordered regions ( X 2 1 ) .Small-angle and wide-angle x-ray scattering were used by Khambatta and Stein ( X 1 3 )to study PVC-poly-e-caprolactone blends. X-ray diffraction and electron diffraction were used by Markova et al. (X16),to study short-range order in amorphous and crystalline polymers. The heating of a high density polyethylene melt was accompanied by a change of macromolecular packing from orthorhombic symmetry in the crystalline polymer to hexagonal packing in the melt. Schultz and Long ( X 3 0 ) described an apparatus for rapid energy scanning of small-angle x-ray scattering of polyethylene. The degree of crystallinity and the state of order in polyethylene was determined from wide-angle x-ray diffraction patterns ( X 9 ) . Shimamura and co-workers ( X 3 1 ) measured the intensities of small-angle x-ray scatterings from hot drawn high density polyethylene. Low-angle and wide-angle x-ray dif-

LITERATURE CITED

(1) Brandrup, J.; Immergut, F. H.; McDoweil, W.; "Polymer Handbook"; Wiley-Interscience, New York, 1975. (2) Plastics-General Test Methods and Nomenclature, ASTM Annual Standards, American Society for Testing Materials, Vol. 35, 1976. (3) Plastics-Materials, Film, Reinforced and Cellular Plastics; Fiber composites, ASTM Annual Standards, American Society for Testing Materiais, Vol. 36, 1976. (4) Food Additives Amendment of 1958, September 6, 1958, Public Law 85-929, 72 Stat. 1784, Superintendent of Documents, US. Government Printing Office, Washington, D.C. (5) Code of Federal Regulations,Title 21, Chapter I, Part 121, Subpart F. Published by Office of the Federal Register, National Archives and Records Service, General Services Administration, Washington, D.C., 1976. (6) FDA Guidelinesfor Chemistry and Technology Requirements of Indirect Food Additive Petitions, Bureau of Foods, Food and Drug Administration, Department of Health, Education, and Welfare, Washington D.C., March 1976. General Methods ( A I ) Acosta, J. L.; Sastre, R.; Rev. Plast. Mod. 1975, 29(224), 212-15. (A2) Adeiman, R. L.; Ferguson, R. C.; J. Polym. Sci., Polym. Chem. Ed. 1975, 13(4), 891-911. (A3) Bello, A,; Barrales-Rienda, J. M.; Guzman, G. M.; Polymer Handbook, 2nd ed. 1975, IV, 175239. Ed. Brandrup, J.; lmmergut E. H. Wiiey, New York.

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fraction measurements were made on solution crystallized hi h density polyethylene ( X 3 3 ) . %as Gupta and Noon ( X 8 )used high-field x-ray diffraction and infrared studies a t low temperatures to show that the nucleation of small crystalline regions in polyethylene occurred owing to the removal of defects from the paracrystalline boundary. Rybnikar ( X 2 8 )determined the crystallinity of branched polyethylene from x-ray diffraction patterns in which the diffraction curve corresponding to the amorphous fraction was obtained by linear extrapolation of the scattering intensity of the melt as a function of the temperature. Ooi e t al. ( X 2 3 ) attributed both the 17- and 9-line ESR spectrum of y-irradiated isotactic polypropylene and the 6line spectrum of atactic polypropylene to the CH&MeCHzradical. High-angle x-ray diffraction studies of atactic poly( 1-methylhexamethylene),poly( 1-methyloctamethylene), poly( 1-methyldecamethylene), and poly( 1-dodecamethylene) revealed a partial intra- and intermolecular order suggesting that the above named copolymers may be considered as ethylene-propene copolymers containing along the chains 2 , 3 , 4, and 5 ethylene units for every propylene unit respectively (X4). Low- and wide-angle x-ray diffraction patterns indicated that aqueous gels of hexadecyl vinyl ether-maleic anhydride copolymer were lamellar at low degrees of neutralization and cylindrical at high degrees of neutralization ( X 3 2 ) .Based on small-angle measurements, Mueller ( X 2 0 ) observed that the number of crystallites and the maximum crystalline volume of amorphous poly(ethy1ene terephthalate) annealed at 100-80 "C was a function only of temperature. The kinetics of reordering of poly(ethy1ene terephthalate) from the glassy amorphous state and from the melt were recorded as a function of temperature ( X 2 7 ) .Two crystalline modifications in poly(ethy1ene terephthalate) were indicated by x-ray diffractograms prepared by Razumova et al. ( X 2 5 ) .Alter and Bonart ( X I ) showed that poly(l,4-butylene terephthalate) has a kinked chain conformation with a tri-clinic unit cell. Electron diffraction and electron microscopy data on poly(metallophenylsi1oxanes) indicated that the nature of the metal affected the degree of crystallinity, type of crystal lattice, and the packing density (X14).Steiner ( X 3 2 )measured the cure in urea-formaldehyde resins from the x-ray pattern of the dried resins treated with bromine in carbon tetrachloride. The bromine content of the product correlated closely with the number of HOCH2- groups.

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Infrared and Raman Spectrometry

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