S. Katz, W. W. Pin, Jr., and G. J. Jones, Jr., Ciin. Chem., 19, 817 (1973). R. A. Krause and D. H. Busch, Anal. Chem., 30, 817 (1958). R. Lang and H. Kurtenacker, Fresenius' Z. Anal. Chem., 123, 169 (1942); Chem. Abstr., 37, 3016. E. Blasius, G. Horn, A. Knochel, J. Munch, and H. Wagner in "Inorganic Sulphur Chemistry", G. Nickiess. Ed. Elsevier, Amsterdam, 1968, Chap. 6. R. A . Henry, J. A. Schmit, and R. C. Williams, J, Chromatogr. Sci., 11, 358 (1973).
J. H. Knox and G. Vasvari, J. Chromatogr. Sci., 12, 449 (1974). L. R. Snyder and J. J. Kirkland. "Introduction to Modern Liquid Chromatography", John Wiley & Sons, Inc., New York, NY, 1974, Chap. 9. 122) M: Schmidt and T. Sand, J. inorg. Nucl. Chem., 26, 1173 (1964). (23) A. W. Wolkoff and R. H. Larose, Canada Centre for Inland Waters, Burlington, Ontario, unpublished work, 1974.
RECEIVEDfor review October 15, 1974. Accepted January 24, 1975.
Determination of Etherification Levels in Acrylamide Interpolymers Using A Icohol Exchange-Ga s Chromatographic Techniques D. G. Anderson, K. E. Isakson, J. 1.Vandeberg, M. Y. T. Jao, D. J. Tessari, and L. C. Afremow DeSoto, h c . 1700 S. Mi. Prospect Road, Des Plaines, lL 600 18
A quantitative method for the determination of alkoxylation levels in acrylamide interpolymers was developed using alcohol exchange followed by gas chromatographic analysis of the reaction products. The importance of controlling the removal of solvents from the polymer samples prior to analysis is described and a recommended procedure given. Optimum catalyst levels to ensure complete alcohol exchange with 2-ethyl hexanol are reported. This procedure permits the determination of alkoxyl groups in a polymer system without interference from ester groups along the polymer backbone.
Etherified alkylolated thermosetting acrylamide interpolymers have the general structure:
EXPERIMENTAL
R
I
fCH,-CH)jifCH,-CCCH,-CHk
I
c=o I NH - R"
I
c=o I
I
0
OR1
where: R = H or CH, RI = H, CH, ,CH ,, C4Hg or C,H, R"= H, CH20C4Hgor CH20H These polymers are desirable base resins for use in appliance coatings, aluminum coil coatings, and metal decorating finishes. Their popularity is largely a result of superior properties including: better flexibility and fabrication a t a given hardness, high degree of hardness, good exterior durability, improved chemical and stain resistance properties, and good color and gloss retention (1-4). A critical compositional limitation of these polymers is the type and quantity of etherifying alcohols present. Therefore, a reliable analytical technique is needed to give this information. A procedure for the determination of etherifying alcohols in acrylamide polymers has not been reported in the literature. An alcohol exchange procedure in conjunction with gas chromatography has been presented 1008
to determine the etherifying alcohols in methylolated melamines (5). The Zeisel reaction has been extensively studied and has been used successfully for the determination of alkoxyl groups in cellulosic materials (6-8). Quantitative cleavage of the alkoxy groups in polymers is routinely obtained; however, hydriodic acid also cleaves any ester linkages on the polymer backbone, giving a positive interference (9). The analytical approach employed in this paper enables the identification and quantitation of the etherifying alcohols present in thermosetting acrylamide interpolymers via alcohol exchange when interfering ester linkages are present in the polymer backbone. Calibration standards are not required, and the method is specific, rapid, and accurate. In addition, no interferences are encountered from alkyl esters present in the sample matrix.
ANALYTICAL CHEMISTRY, VOL. 47, NO. 7, JUNE 1975
A p p a r a t u s . Gas chromatographic separations were performed using a Hewlett-Packard 5750 gas chromatograph equipped with flame ionization detectors. A 12-ft X 0,125-in. 0.d. stainless steel column was packed with 20% Carbowax 20M on 60-80 mesh GasPak WAB. T h e helium flow rate was 20 ml/min with an inlet pressure of 65 psi. Injection port and detector temperatures were 220 and 240 "C, respectively. The column temperature was held a t 105 "C until the elution of the pentanol peak, then programmed from 105 to 205 "C a t 15 "Cimin and held until the 2-ethylhexanol eluted. The glass assembly used to carry out the alcohol exchange reaction was purchased from Ace Glass, Inc. I t consists of a 50-ml erlenmeyer flask equipped with a 3 14/20 joint (Ace Glass 9290), topped with a Liebig condenser with a 3 14/20 joint (Ace Glass 9195). All radioactive tracer studies were performed by Shell Chemical Company (IO) using a Tricarb liquid scintillation counter. Reagents. "Reagent grade" 2-ethylhexanol, n- butanol, n- pentanol, butyl cellosolve, and acetone (Eastman Organic Chemicals) were used as received. Paraformaldehyde, p - toluenesulfonic acid, and propionamide (Eastman Organic Chemicals) were used without further purification. Shell Chemical Company supplied the butanol-14C and Z - b u t o ~ y e t h a n o l - ~ ~All C , polymers were synthesized by the Resin Development Department of DeSoto, Inc. and dried as outlined in the Procedure section of this paper. These polymers were prepared to have 100% etherification of the acrylamide present. P r o c e d u r e . Drying of Polymer Samples All acrylamide interpolymer samples were initially diluted to 10% nonvolatile resin with acetone. Thin films of the resin solutions were uniformly cast on clean glass plates using a smooth glass rod and immediately dried a t 50 OC under 5 cm Hg for 2.5 hours to remove all solvents. T h e film thickness of the dried polymers was kept below 0.5 mil to
ensure complete solvent removal. The films were removed from the glass plates using oil free razor blades and stored in vials. Molecular weight distributions of the polymer solutions and the dried polymers were determined using gel permeation chromatography. No evidence of fractionation or curing of the polymers during the drying steps was observed. Alcohol Exchange Reaction. The etherifying alcohols present in the polymer backbone were exchanged according to the reaction: 4 H 2 4 H -
I I NH
