Supplementary Information for Blocky Sulfonation of Syndiotactic Polystyrene: A Facile Route Toward Tailored Ionomer

Transcription

1 Supplementary Information for Blocky Sulfonation of Syndiotactic Polystyrene: A Facile Route Toward Tailored Ionomer Architecture via Post-Polymerization Functionalization in the Gel-State Gregory B. Fahs, Sonya D. Benson, and Robert B. Moore* Table S1. Kinetic parameters at 220, 225, 230 and 235 C for SsPS3.2H + R and SsPS3.2H + B. SsPS Kinetic Parameter 220 C 225 C 230 C 235 C SsPS3.2H + R t½ (min) n K (min -1 ) 7.9 x x x x 10-3 SsPS3.2H + B t½ (min) n K (min -1 ) 3.2 x x x x 10-3 S1

2 Figure S1. DSC thermograms for sample preparation procedure used in scattering experiments. Heat flow versus temperature of sps (H), SsPS3.5H + B (B), and SsPS3.2H + R (R) post-isothermal crystallization at 220 C, 225 C, 230 C, and 235 C for 1 hour using a heating rate of 10 C/min. S2

3 Figure S2. ln [-ln (1-Xc(t))] versus ln t at 220, 225, 230, and 235 C for (R) SsPS3.2H + R and (B) SsPS3.5H + B. Fit lines are shown in black in the graph used to determine the Avrami parameters shown in Table S1. S3

4 WAXD was used to probe the polymorphic composition of the copolymers in comparison to the sps homopolymer. Using WAXD, the polymorphic composition of each system can be determined by comparing the relative peak areas of the diffraction peaks appearing at 11.6 and 12.2 using the following empirical relationship derived by Guerra, =.. /... /. 100 (3) where P α represents the fraction of crystallites in the α-form and. and. are the integrated areas of the diffraction peaks occurring at 2θ=11.6 and 12.2 degrees respectively. 1 Figure S3 shows the WAXD data for sps and the SsPS3.5H + Random and SsPS3.2H + Blocky copolymers that were isothermally crystallized at temperatures ranging from 220 o C to 235 C. Figure S4 compares the polymorphic compositions of the polymers over the same range of isothermal crystallization temperatures. For pure sps, a decrease in P α with increasing crystallization temperature is commonly observed, 2 and this trend is clearly observed for each of the samples in this study. In agreement with our previous studies, the incorporation of sulfonic acid functionalization is found to promote the formation of the β polymorph in both the random and blocky SsPS copolymers. This behavior was attributed to restricted segmental mobility in the melt due to the interacting sulfonate groups, thus inhibiting the formation of the kinetically favored α-form crystals. 3 In comparing the polymorphic composition of the sulfonated copolymers, it is surprising to note that the SsPS3.2H + Blocky sample displays a much stronger tendency to promote the formation of the β polymorph, relative to the random analog at an equivalent sulfonate content. Given the proposed blocky architecture for the gel-state sulfonated copolymer, it is reasonable to expect that the local mobility of the crystallizable segments (well separated from the functionalized units) would be somewhat greater than that of the statistically shorter S4

5 crystallizable segments in the random analog (containing a more homogeneous distribution of sulfonate groups). Thus, the mobility argument (used to rationalize the inhibited formation of the kinetically favored α-form crystals for each of the SsPS copolymers over that of pure sps) is not feasible to explain the enhanced β form composition observed for the SsPS3.2H + Blocky sample. As an alternative hypothesis, we consider the metastable nature of the α-polymorph. 4 Woo and coworkers found that sufficiently small α-form lamella can gradually transform into the β phase during isothermal crystallization provided that the crystal thickness is limited to below a critical size. 5 Moreover, this α to β transformation was proposed to occur through a lamellar thickening process. If the blocky architecture of the SsPS3.2H + Blocky copolymer limits the size of the α-form lamella over that of pure sps, then these small metastable crystallites could be susceptible to solid-solid transformation, leading to an increase in the composition of the thermodynamically stable β phase. Of course, this size restriction is also likely to occur for the SsPS3.5H + Random copolymer. However, it is also reasonable to expect that lamellar thickening would be limited in the random analog due to structural pinning from the local proximity of defects (i.e., the sulfonated units) along the statistically shorter crystallizable chain segments. With limited lamellar thickening, the α-form lamella in the SsPS3.2H + Random would persist, and perhaps grow laterally, leading to higher P α composition, relative to the blocky analog. Clearly, this prospective argument will require further analysis (beyond the scope of this initial study) in order to support the link between the polymer architecture and polymorphic composition. S5

6 Figure S3. WAXD profiles of sps, SsPS3.2H + R (R), and SsPS3.2H + B (B) post-isothermal crystallization at 220 C, 225 C, 230 C, and 235 C for 1 hour. S6

7 Figure S4. Percentage of α-crystallites (P α ) versus isothermal crystallization temperature; samples were crystallized for 1 hr. Polynomial fit lines have been added as visual guide. References 1. Guerra, G.; Vitagliano, V. M.; De Rosa, C.; Petraccone, V.; Corradini, P. Polymorphism in melt crystallized syndiotactic polystyrene samples. Macromolecules 1990, 23 (5), Woo, E. M.; Sun, Y. S.; Yang, C. P. Polymorphism, thermal behavior, and crystal stability in syndiotactic polystyrene vs. its miscible blends. Progress in Polymer Science 2001, 26 (6), Orler, E. B.; Moore, R. B. Influence of Ionic Interactions on the Crystallization of Lightly Sulfonated Syndiotactic Polystyrene Ionomers. Macromolecules 1994, 27 (17), Keller, A.; Cheng, S. Z. D. The role of metastability in polymer phase transitions. Polymer 1998, 39 (19), Ho, R.-M.; Lin, C.-P.; Tsai, H.-Y.; Woo, E.-M. Metastability Studies of Syndiotactic Polystyrene Polymorphism. Macromolecules 2000, 33 (17), S7