I n d . Eng. C h e m . Res. 1995,34, 2598-2604
2598
Functional Polymers Prepared from p-Styrenesulfonyl Chloride as the Functional Monomer Karel Jei.Bbek* and LibulSe Hankovh Institute of Chemical Process Fundamentals, Academy of Sciences of the Czech Republic, 165 02 Prague 6, Czech Republic
Andre Revillon Laboratoire des Materiaux Organiques a ProprietCs SpCcifiques CNRS, BP 24, 69390 Vernaison, France
Properties of the functional polymers prepared from functional monomers and those into which the active groups were introduced by a suitable polymer-analog reaction could differ substantially, especially in the active group distribution. In this paper are analyzed specific properties of functional polymers prepared by copolymerization of p-styrenesulfonyl chloride (SSC) with divinylbenzene and styrene. There was determined the polymerization activity of SSC. Resulting Alfrey-Price scheme parameters for SSC are &I = 0.73 and el = 0.58. The swollen-state morphology of a series of polymers prepared in the presence of various solvents was investigated by inverse steric exclusion chromatography both before and after hydrolysis of the sulfochloride groups. Obtained results suggest that copolymerization of SSC with styrene and divinylbenzene does not produce polymers composed from randomly alternating monomer units but rather copolymers consisting of functionalized and unfunctionalized domains resulting from a possible phase separation of SSC-rich domains due to the strong mutual interaction of the functional monomer molecules or polymer segments.
Introduction For preparation of functional polymers basically two possibilities exist. More frequently, the active groups are introduced into the preprepared polymer matrix by a suitable polymer-analog reaction. Modifications of styrene-divinylbenzene by a large number of various methods are the most notable examples of this route. The second possibility is to polymerize or copolymerize monomers already containing the desired functionality or its precursor. Here the noticeable examples are preparation of weak acidic ion exchangers using acrylic acid or its esters, and anion exchangers based on vinylpyridine. Each of these methods has its specific advantages and drawbacks and their products, even if quite similar from the chemical point of view, may differ substantially, e.g., in the distribution of active groups or in the morphology. We decided to investigate the specific properties of functional polymers prepared by copolymerization of the functional monomer p-styrenesulfonyl chloride (SSC) with divinylbenzene (DVB)and styrene (SI. SSC is
CH = CH2
ssc
Q SO2CI
relatively new functional monomer of a lypophilic nature, freely miscible with other oleophilic monomers like S or DVB. Sulfonyl chloride groups in the resulting polymer can be converted by hydrolysis into the strongly acidic centers, the same functionality as produced by sulfonation of styrenic polymers. This offers the possibility of a convenient assessment of differences be-
* To whom correspondence should be addressed. E-mail address:
[email protected]. 0888-5885/95/2634-2598$09.~OJ0
tween functional polymers prepared by the polymerization of a functional monomer and the well-known conventional sulfonated resins. The greatest difference should be expected in the distribution of the functional groups. It is well-known that sulfonation of the S-DVB copolymers proceeds layer by layer from the surface to the interior of the polymer mass (Wheaton and Harrington, 1952). Hence, in a partially sulfonated styrenic polymer only fully sulfonated or completely unsulfonated domains can exist. The copolymerization of SSC with DVB or S can lead to a polymer in which the functionalized and unfunctionalized units will be mutually intermixed. Usual tools for modification of the morphology of polymeric carriers, such as content of the cross-linker (DVB) or addition of cosolvents t o the polymerization mixture could have in the SSC copolymers different effects than in the well-studied S-DVB copolymers. Distribution of DVB and SSC units in the polymer depends on the ratio of the polymerization activity of SSC and other comonomers. Effect of cosolvents on the morphology of the resulting polymer differs according to the affinity of the solvent and the polymer chainswhether they are swelling or precipitating solvents for a given polymer (Jefabek et al., 1992). Solvents which swell S-DVB copolymers need not have the same effect on the poly-SSC or chain segments with high content of this monomer. The influence of these factors should be apparent in the swollen-state morphology of the polymers. For investigation of these phenomena we used inverse steric exclusion chromatography (ISEC) (Halasz, 1975; Freeman, 1977). In this method the investigated material is used as the stationary phase in the chromatographic column and the elution volumes of standard solutes with known molecular size are measured. The porosity evaluation is based on the modeling of the real morphology as a set of discrete pore fractions, each characterized by its pore size (Jefabek, 1985a,b). Mathematical treatment of the chromato-
0 1995 American Chemical Society
Ind. Eng. Chem. Res., Vol. 34, No. 8, 1995 2599 Table 1. Composition of the Polymerization Mixtures in Preparation of the Set of Polymers polymer monomer mixture composition, mol % no. SSC stvrene+EVB DVB
1 2 3
4 5 6 7 8 9 10 11 12 13 14 15
96 23 23 46 46 89 89 89 89 43 43 41 41 41 37
2 73 73 50 50 5 5 5 5 49 49 41 41 41 28
2 4 4 4 4 6 6 6 6 8 8 18 18 18 35
added solvent= ACN T ACN T ACN T Bu T+pTSC, 1:l ACN T ACN T Bu T
a Solvents added to the polymerization mixture in the amount 2/3 of the weight of the monomers. ACN, acetonitrile; T, toluene; Bu, 2-butanone; pTSC, p-toluenesulfonyl chloride. Weight of the reaction mixture for preparation of the individual polymers was 20-30 g.
graphic data then provides information on volumes of individual model fractions. Series of copolymers of SSC with various amounts of S and DVB, both before and after the hydrolysis of the sulfonyl chloride groups, was investigated by the ISEC alternatively in organic and aqueous environments.
Experimental Section Polymer Preparations. p-Styrenesulfonyl chloride (SSC) was prepared by reaction of sodium p-styrenesulfonate (Aldrich-Chemie) with thionyl chloride in anhydrous dimethylformamide using a procedure described in the literature (Kamogava et al., 19831, except that in the final extraction of the mixture of water and the reaction products benzene was replaced by toluene. Solvent removal was performed a t ca. 45 "C with an oil vacuum pump. According t o the NMR analysis, resulting product contained 88.6 wt % SSC (rest toluene). SSC is hydrolytically stable enough t o be purified during the preparation by washing with water. Nevertheless, we were afraid that if the polymerization was performed in suspension, the prolonged expositure of the polymerization mixture to the aqueous environment could result in a partial hydrolysis of either the SSC monomer or the sulfochloride groups in the polymer. Therefore, the SSC-containing polymers were prepared by bulk polymerization in sealed ampules. For investigation of possibilities to modify the morphology of the resulting polymers and t o facilitate their crushing, solvents of various nature were added to the polymerization mixture. The mixture of monomers (SSC, technical (55%) divinylbenzene (DVB)and styrene) in the desired ratio (see Table 1) with 3% of dibenzoyl peroxide and the solvent (total weight of the charge 2030 g) was sealed in glass vials, immersed in an oil bath, and heated to 75 "C for 12 h. The polymers obtained were gently ground with mortar and pestle, extracted in soxhlet extractor with acetone for at least 6 h, and sieved for the 125-250 pm range to be used in the ISEC experiments. Determination of the PolymerizationActivity of SSC. There were prepared mixtures of monomers 5 cm3 each, containing SSC and styrene in various ratios. To each mixture was added 15 cm3 of toluene containing
0.05 g of dibenzoyl peroxide. Mixtures were immersed into the oil bath a t 70 "C. To limit possible influence of inhomogenity of the polymerization environment on the kinetics, immediately after the appearance of the first traces of spontaneous precipitation of the polymer, the reaction was stopped by addition of 1 cm3 of toluene containing 0.15 g of di-tert-butylphenol. The polymer products were isolated by precipitation by the mixture of 99 vol of methanol and 1 vol of concentrated hydrochloric acid. However, it was found that at these conditions only conversions lower than 1%were achieved. For the next series of measurements, 2-butanone as the solvent was chosen, otherwise the conditions were the same. Polymerization was performed till the first appearance of a haze in any of the mixtures (ca. 50 min). Then the polymerization was stopped by addition of the inhibitor and polymers were isolated by precipitation. The isolated polymers were washed with methanol and dried overnight at 80-90 "C. The composition of the polymers was evaluated by sulfur determinations. ISEC Measurements. Swollen-state morphology of the unhydrolyzed polymers containing sulfochloride groups was characterized by the ISEC in tetrahydrofuran using n-alkanes and polystyrenes as standard solutes. Morphology of the water-swollen hydrolyzed polymers in the Na' form was characterized using 0.2 M sodium sulfate solution as the mobile phase and heavy water, sugars, and dextrans as standard solutes. The porosity evaluation is based on the modeling of real morphology as a set of discrete pore fractions, each characterized by its pore size. The evaluation of macropores (d, > 10 nm) was based on the cylindrical pore model with pore diameter as the pore size characteristic parameter. For the description of morphology of swollen polymer mass was used the Ogston model (Ogston, 1958) depicting the pores as spaces between randomly oriented cylindrical bodies. In this model, the parameter characterizing the pore size is the density C of the cylindrical bodies representing the polymer chains, expressed in units of length per unit of volume, i.e., nm-2. The treatment of chromatographic data then provides information on volumes of individual model fractions. Details of the experimental procedure and data treatment were reported elsewhere (JeFabek, 1985a,b). Hydrolysis of the Sulfonyl Chloride Groups and the Exchange Capacity Determination. The sulfonyl chloride groups (-SO2Cl) were converted into the sodium sulfonate groups (-S03Na) by alkaline hydrolysis. Specific conditions used will be described in the Discussion section. Before the determination of the resulting exchange capacity the hydrolyzed resins were converted into the Hf form by washing with excess hydrochloric acid and then they were washed by deionized water till negative reaction for C1- ions (AgNO3). The exchange capacity was then determined by the direct potentiometric titration of the suspension of the resin in 0.1 N KC1 solution. Results and Discussion Polymerization Activity of SSC. Results of the experiments designed for to determine polymerization activity of SSC in relation to styrene are shown in Table 2. For further mathematical treatment the data on the monomer composition were corrected for the drif%during the copolymerization (Hart, 1961). The corrected value M Iis mean of the mole fractions of monomer 1 at the
2600 Ind. Eng. Chem. Res., Vol. 34, No. 8, 1395 Table 2. Starting Compositions of the Monomer Mixtures, Conversion and Composition of the Polymers sulfur in mole fraction of monomer mole fraction of conversion of monomers, wt % polymers, wt % SSC in polymers mixture SSC in monomers 0.064 0.119 0.206 0.336 0.455 0.582 0.712
6.4 7.6 9.2 10.5 11.6 12.6 13.5
4.6 6.7 9.5 11.7 11.8 13.5 9.6
1.o
0.258 0.323 0.415 0.506 0.585 0.675 0.757
/I
0.8
.-
8 0.6
g$ C
8c
0.4
L
H 0.2
0.0
0.8 1.o Molar fraction of SSC in monomers Figure 1. Copolymerization of p-styrenesulfonyl chloride (SSC) with styrene. 0.2
0.0
0.4
0.6
0.75
I
0.12
0.16
0.20
r2 Figure 2. Joint confidence region of copolymerization parameters r1 and r2 computed on the 95% probability level.
beginning and the end of copolymerization, respectively:
+
M , = (M,’ M1”)/2
(1)
M1”= (AM,’ - BP,)/(A - B )
(2)
tions
e , = e2 f (-In r1r2Y2
Q1= In QZ - e2(e2- e , )
where
+ M,’W2) B = x/(P,Wl + P2W2)
A = 100/(M,’W,
(3) (4)
(1, SSC; 2, styrene) in the copolymer, W1 and WZ are the molecular weights of the monomers, and 1c is the conversion of the monomers (in wt %). The instantaneous copolymer composition is given by the equation:
(r,
+
+
(rl - I)M,~ M , r2 - 2 ) ~ +~2(1 ’ - r 2 ) ~+1r2
(7)
7.2
P1 and P2 are the mole fractions of the two monomers
P, =
(6)
(5)
Values of r1 and r2 are determined by nonlinear regression using Marquardt’s algorithm for the minimization of the sum squared of differences between theoretical and experimental values of PI. The least sum of squared error corresponds to rl = 0.93 and r2 = 0.16. Correlation of the polymer and monomer compositions using these values of the reactivity parameters is shown in Figure 1, and in Figure 2 is shown the joint confidence region of the rl and r2 parameters determined on the 95% probability level. The Alfrey-Price reactivity (&I)and the double bond polarity (el) parameters were computed using the equa-
with standard values for styrene Q2 = 1.0 and e2 = -0.8. Alfrey-Price scheme parameters for SSC are Q1 = 0.73 and el = 0.58. A much higher value of the polarity parameter e for SSC than that for styrene is indication of a powerful influence of the strong electron captor substituent in the para position on the polarization of the vinyl double bond. A similar effect was observed also in the case of p-styrenesulfonyl fluoride (Hart, 1961). Morphology of the Unhydrolyzed Polymers. Inverse steric exclusion chromatography (ISEC)gives insight into swollen polymer gel morphology and makes it possible t o assess important features of functional polymers, not always discernible from data on composition. The monomer mixture for polymer 1 (see Table 1)was prepared from SSC and technical DVB in the amount corresponding to 2% pure DVB in the mixture. After hydrolysis of the polymer, the resulting material from the chemical point of view should be close t o the conventional ion exchanger prepared by sulfonation of the styrenic copolymer containing the same amount of DVB. In Figure 3 are compared distributions of the polymer chain density of unhydrolyzed polymer 1 determined by ISEC in tetrahydrofuran and hydrolyzed polymer 1and a conventional sulfonated ion exchanger with the same DVB content determined in the aqueous
Ind. Eng. Chem. Res., Vol. 34,No. 8,1995 2601
-
Waler-smllen sulfonated ion em:hanger cont 2 % DVB
7 - I
Fraction volume, cm-319
Water-smllen hydrolyzed polymerNo. f
Fraction volume,
-0.5
cm-3
Pol
THF-smllen unhydrolyzed polymerNo. 1
P -0 0.1 0.1
0.2 0.5 1 2 Polymer chain density C, nm^-2
0.2
0.5
1
2
Polymer chain density C, nmk2
Figure 3. Comparison of swollen-state morphologies of unhydrolyzed and hydrolyzed SSC polymers with 2% DVB and conventional sulfonated ion exchanger with the same nominal crosslinking.
Figure 4. Swollen-state morphologies of SSC polymers prepared in the presence of different solvents. Polymer 6, toluene; polymer 7, acetonitrile; polymer 8,2-butanone; polymer 9 , l : l toluene and p-toluenesulfonyl chloride.
environment (Jelabek and Setinek, 1990). In polymer 1two regions are apparent differing widely in polymer chain density. The relatively small volume of the fraction with C = 0.1 nm-2 contains very little of the polymer mass. Most of the polymer is concentrated in the fraction with a high polymer chain density C = 1 nm-2, much less swollen than the conventional sulfonated polymer with the same DVB content, whose morphology is represented by a single, highly swollen fraction with low C = 0.2 nm-2. This suggests that in polymer 1 is the mobility of the polymer chains determined not only by the number of covalent cross-links but probably also by a quite significant physical crosslinking resulting from the chain entanglement created during polymerization of relatively strongly associated molecules of reactive monomer. This effect was already observed in polymerization of another reactive monomer, vinylpyridine (Jelabek et al., 1993). Mutual entanglement of the polymer chains during their growth can be influenced by presence of solvents in the polymerization mixture. Most of the polymers synthesized in this study were prepared in the presence of various solvents, used not only in an attempt to modify the morphology, but also to facilitate the dissipation of the polymerization heat. In the absence of solvents it was difficult to keep the bulk polymerization process from running out of control due to internal heat development. In most cases the solvent addition to the polymerization mixture is associated with the creation of macropores resistant to drying. All the polymers prepared in this study were opaque, which is a sign of the presence of porosity. However, in the dry state substantial BET surface area was found only for polymers 15 (140 m2/g) and 13 (20 m2/g). All other polymers shown negligible surface area (less than 1 m2/g). Results of the ISEC investigation in agreement with these findings, as in the region of macropores (pores with diameter 10- 100 nm) significant porosity was detected also only in polymers 15 and 13. In all other polymers the ISEC show only porosity in the region associable with swollen polymer mass. For copolymers of styrene and divinylbenzene the effect of solvent addition on the swollen-state morphology determined by ISEC was demonstrated on toluene and acetonitrile (JeFabek et al., 1992). Acetonitrile as precipitating solvent for this type of polymer promotes creation of poorly swellable polymer mass, and in the swollen-state morphology of the resulting polymers lowdensity fractions of polymer mass are not represented.
Toluene solvates the styrenic polymer chains and prevents their mutual entanglement during polymerization. In the swollen-state morphology of the resulting polymer appear beside the dense fractions also some more highly swellable domains with C -c 1 nm-2. On the Figure 4 are compared the morphologies of the tetrahydrofuran-swollen unhydrolyzed SSC polymers containing 6% DVB, prepared alternatively with acetonitrile (polymer 6), toluene (polymer 7), 2-butanone (polymer S), and mixture of toluene and p-toluenesulfonyl chloride (polymer 9) as modifjring solvents. In the morphology of the polymers prepared in the presence of both toluene and acetonitrile practically only the dense, poorly swellable fractions were detected. These solvents act in relation to the SSC polymers as precipitants. For toluene this conclusion is corroborated by the experience from the above discussed determination of the polymerization activity of SSC, when in the series using toluene as the solvent, the first precipitated polymer appeared already at monomer conversion around 1%.However, even 2-butanone, which was able to keep the SSC polymer in solution up to much higher monomer conversions, did not produce a notably better swellable polymer morphology. As in the case of another reactive monomer, vinylpyridine (Jelabek et al., 1993), the strong mutual interactions of the SSC monomer or polymer molecules were effectively disturbed only by the similar, but unpolymerizable molecules of p-toluenesulfonyl chloride. Only in the presence of this additive was it possible to create a significantly more expandable network. Hydrolysis of the SSC-Containing Polymers. Hydrolysis of the sulfochloride group was performed in alkaline solution. By periodic checking of the alkali content changes during the hydrolysis in selected cases was followed the kinetics of the reaction. To facilitate the swelling, especially of the unfunctionalized parts of the skeleton, these experiments were performed in a 1:l mixture of dioxane and water 1:l. Results are shown in Figure 5. Polymers 6, 7, and 9 with a high content of the hnctional monomer were hydrolyzed very rapidly. The easiest was the hydrolysis of polymer 9 for which the ISEC results discussed above shown the most swellable morphology. Highly cross-linked polymer 15, containing less than 40 mol % SSC monomer, was hydrolyzed much more slowly, but nevertheless, even in this case the degree of hydrolysis seems to proceed to a defined limiting value. Influence of the presence of unhnctionalized domains in the polymer was especially apparent if the hydrolysis
2602 Ind. Eng. Chem. Res., Vol. 34,No. 8, 1995
80 3
EJ
E
0 0
Polymer9 Polymer 15
-
v
6%DVB
-Inh
0
2
0
18%DVB 35 Yo DVB
60 vi
.-In
e
40
A
c
1
0
I
1
I
I
I
50
100
150
200
250
300
0
Time, min
Figure 5. Kinetics of hydrolysis of sulfochloride groups in selected polymers. Table 3. Exchange Capacities Achieved after Alkaline Solution Hydrolysis of the Polymers in Water and in 3:l Mixture of Water with Dioxane
ssc exchange capacity after hydrolysis polymer content, theoretical: in water,b in dioxane/water: no. mol% mmoVg mmoVg mmoYg 1 2 3 4 5 6 8 10 11 12 13 14 15
96 23 23 46 46 89 89 43 43 41 41 41 37
5.27 1.86 1.86 3.23 3.23 5.01 5.01 3.05 3.05 2.89 2.89 2.86 2.58
4.27 0.98 0.82 0.57 0.53
o /
4.73 0.47 0.68 2.14 2.53 4.53 4.45 1.84 2.11 1.53 1.60 1.67 1.20
Computed from the SSC content. 2% NaOH in water, 40 "C, 3 h. 2% NaOH in 1:3 wateddioxane, 40 "C, 3 h.
was performed in the absence of dioxane. In purely aqueous alkaline solution it was possible to hydrolyze to a high degree only the polymers with low amount of the unfunctionalized polymer mass (Table 3, polymer 8). In the polymers containing a greater part of unfunctionalized monomers was only a fraction of the sulfochloride groups was accessible for hydrolysis in water (Table 3, polymers 10-12 and 15). Evidently, the unfunctionalized styrenic polymer unable t o swell in water envelopes some of the sulfochloride group domains and prevents their hydrolysis. To achieve the highest possible hydrolysis degree, the reaction was finally performed in 2% sodium hydroxide solution in a mixture of dioxane with water (3:l) for 4 h at 40 "C. The obtained exchange capacities of the resulting resins are listed in the last column of the Table 3. Nevertheless, even at these conditions, it was not possible to hydrolyze all the sulfochloride groups. In Figure 6 are the obtained hydrolysis degrees (computed as percents of the theory based on the polymer composition) plotted against SSC content in the polymers. It is evident that there is a clear correlation between these two quantities, which is not disturbed by the differences in the DVB content of the polymers. The mobility of
I
1
I
1
20
40
60
80
100
SSC content in the polymer, mol % Figure 6. Dependence of attainable hydrolysis degree on SSC content in polymers with various nominal degrees of cross-linking.
the chains in the investigated polymers seems to be determined much more by the influence of the polymer composition than by the number of cross-link bonds. Most probably, it is due to the extensive entanglement of the chains created in the polymerization process as a result of the high mutual affinity of the SSC units. Morphology of the Hydrolyzed Polymers. ISEC measurements generally require that the elution behavior of the solutes used for the probing of the pore space should be determined by steric effects only. Suitable selection of the mobile phase (tetrahydrofuran for the lipophilic and 0.2 M aqueous sodium sulfate solution for the hydrophilic polymers) and standard solutes (n-alkanes and polystyrenes, or sugars and dextrans) makes it possible to fulfill this requirement reasonably well for the purely lipophilic or purely hydrophilic polymers (Freeman and Schramm, 1981; Crispin and Haldsz, 1982). However, the investigated polymers after hydrolysis contain both the lipophilic unhydrolyzed or unfunctionalized domains and the hydrolyzed, hydrophilic parts of the polymer mass. Fortunately, these polymer domains differ in their ability to swell. When the strongly acidic groups of the hydrolyzed polymer are neutralized with metal cations, they are not able to be solvated by organic solvents and the polymer parts bearing these groups do not swell in the organic solvents. Similarly, the lipophilic domains do not swell in the aqueous environment. In the partially sulfonated polymer with well-defined waterswellable functionalized and organic solvent swellable, unfunctionalized domains, by the ISEC investigation alternatively in THF and water it was possible to characterize the morphology of these domains separately (Jefabek and Setinek, 1989). In the polymer prepared from functional monomers was expected an intimate intermixing of hydrophobic and hydrophilic zones which could complicate a separate swelling of these domains. However, in all but one case it was possible to perform the ISEC measurements of the hydrolyzed polymers (in the Na+ form) alternatively in water and THF without difficulties. All standard solutes were eluted in order of their molecular sizes, and the values of their elution volumes did not suggest a presence of nonsteric interactions with the investigated
Ind. Eng. Chem. Res., Vol. 34,No. 8,1995 2603
Polymer 8
Unhydrolyzed , ISEC in THF
I
1 FracCon volume, cm^3lg
0.5 Hydrolyzed , ISEC inTHF
0
Polymer chain density, nm^-2
Polymer 14
ISEC in T H F
1
ISEC in mater
0.5
Fracfon volume, cm*3/g
ISEC in T H F
0
Polymer chain density, nm^-2
Figure 7. Comparison of swollen-state morphologies of polymers 8 and 14 before hydrolysis in THF and after hydrolysis in water and THF.
polymers. As an example Figure 7 are compared the results of the ISEC investigations of polymers 8 and 14. For polymer 8 before hydrolysis the ISEC measurement in THF showed bidisperse morphology with a substantial volume of polymer fraction characterized by high chain density with C = 2 nm-2 and a small volume of thinner fraction with C = 0.5 nm-2. After hydrolysis, by ISEC in water was detected a similar bidisperse morphology, only better swollen-as reflected in the shift toward lover polymer chain densities. Hydrolyzed polymer 8 in THF showed only a small volume of single fraction of the poorly swollen very dense polymer. This picture corresponds well with the composition of this sample containing 89 mol % SSC and hence, after hydrolysis, only a small part of the lipophilic polymer mass swellable in THF. The polymer 14 contains only 41 mol % SSC, and therefore in the hydrolyzed polymer the shares of the lipophilic and hydrophilic parts should be comparable. The results of the ISEC confirm it, as in both water and THF the hydrolyzed polymer showed substantial volumes of the swollen polymer mass. Observed separate swelling of the functionalized, hydrophilic and the unhnctionalized, lipophilic polymer mass would be hardly possible in a polymer composed from randomly alternating monomer units. This be-
havior is more compatible with a block copolymer morphology consisting of substantial lipophilic and hydrophilic domains. The creation of these separate domains could result from a possible phase separation of SSC-rich domains due to the strong mutual interaction of the functionalizedmonomer molecules or polymer segments. Exceptional behavior in the ISEC investigation in aqueous environment was found with hydrolyzed polymer 15. For ribose there was found a significantly higher elution volume than for the much smaller deuterium oxide. Elution volumes of other sugars (xylose, sacharose, and raffinose) were more or less in the expectable range but dextrans, the more bulkier standards intended for probing the macropores, were strongly adsorbed in this polymer and their elution could not be detected. The observed elution volumes showed clear evidence of nonsteric, specific interaction of the standard solutes with the investigated polymer as the stationary phase. Polymer 15 was prepared from the same parts (by weight) of SSC and technichal DVB. This polymer differs from the rest of the series only in the DVB content, and DVB forms most of the unfunctionalized part of its polymer mass. It is hard to imagine that the high DVB content could introduce any substantial modification of the chemical nature of the polymer in comparison with other samples, and hence, the difference must be in the distribution of the monomer units. If in polymer 15 the functionalized and unfunctionalized units would be really intimately intermixed, the strong adsorption of dextrans on the hydrolyzed polymer could be explained by high probability of concerted, simultaneous lipophilic and hydrophilic interactions between dextran molecules and the polymer surface. On the other polymers, where the ISEC measurements indicate the presence of separate lipophilic and hydrophilic domains, such interaction should be much more scarce. Whether the high interpenetration of the functionalized and unfunctionalized domains was induced in polymer 15 by specific features of the copolymerization kinetics of SSC and DVB or by preclusion of a phase separation of the SSC domains due to steric effects of the DVB cross-links is open to speculation.
Acknowledgment Support for one of the authors (K.J.) during his stay in France from the TEMPRA program administered by the Rbgion RhBne-Apes is gratefully acknowledged. This work was supported in part by Grant No. 104/94/ 0749 from the Grant Agency of the Czech Republic.
Literature Cited Crispin, T.; Halasz, I. Determination of the pore size distribution, by exclusion chromatography, of ion-exchange polymers which swell in water. J. Chromatogr. 1982,239,351. Freeman, D. H.; Poinescu, I. C. Particle porosimetry by inverse gel chromatography. Anal. Chem. 1977,49,1183. Freeman, D. H.; Schram S. B. Characterization of microporous polystyrene-divinylbenzenecopolymer gels by inverse gel permeation chromatography. Anal. Chem. 1981,53, 1235. HalPsz, I.; Martin, K. Bestimmung der poren-verteilung (10-400 A) von festkorpern mit der methode der auschluss-chromatographie. (Determination of pore distribution (10-400 A) in solid materials by exclusion chromatography.) Ber. Bunsen-ges. Phys. Chem. 1975,79,731. Hart, R. Copolymerizaion behavior of m- and p-styrenesulfonyl fluorides. Makromol. Chem. 1961,49,33.
2604 Ind. Eng. Chem. Res., Vol. 34, No. 8, 1995 Jefabek, K. Determination of pore volume distribution from size exclusion chromatography data. Anal. Chem. 198Sa, 57, 1595. Jefabek, K. Characterisation of swollen polymer gels using size exclusion chromatography. Anal. Chem. 1985b,57, 1598. Jefabek, K.; Setinek, K. Structure of macronet styrene polymer as studied by inverse steric exclusion chromatography. J . Polym. Sei. Part A: Polym. Chem. 1989,27,1619. Jefabek, K.; Setinek, K. Strong acidic ion exchangers structure by inverse steric exclusion chromatography. J . Polym. Sci. Part A: Polym. Chem. 1990,28, 1387. Jefabek, K.; Shea, K. J.; Sasaki, D. Y.; Stoddard, G. J. Accessibility of the gel phase in macroporous network polymers: A comparison of the fluorescence probe and inverse steric exclusion chromatography technique. J . Polym. Sci.: Part A: Polym. Chem. 1992,30,605. Jefabek, K.; Widdecke, H.; Fleischer, B. Morphology of swollen copolymers of 4-vinylpyridine and divinylbenzene. React. Polym. 1993, 19, 81.
Kamogawa, H.; Kanzawa, A,; Kadoya, M.; Naito, T.; Nanasawa, M. Conversion of carbonyl compounds via their polymeric sulfohydrazones into alkenes, alkanes, and nitriles. Bull. Chem. SOC.Jpn. 1983, 56, 762. Ogston, A. G . The spaces in a uniform random suspension of fibres. Trans. Faraday SOC.1958,54, 1754. Wheaton, R. M.; Harrington, D. F. Preparation of cation exchange resins of high stability. Ind. Eng. Chem. 1952, 44, 1776.
Received for review October 12, 1994 Revised manuscript received January 19, 1995 Accepted February 6, 1 9 9 P IE940593K Abstract published in Advance A C S Abstracts, J u n e 15, 1995. @
