No abstract

No abstract

No abstract

No abstract

In this study, the mechanical and chemical properties of a series of sulfonated poly(styrene-isobutylene-styrene) (SIBS) block copolymers were evaluated using a combination of nanoindentation, dynamic mechanical analysis (DMA), elemental analysis (EA), Fourier transform infrared spectroscopy (FTIR), water absorption, and small angle X-ray scattering studies (SAXS). The materials properties were characterized as a function of the sulfonation percent in the block copolymers, as well as a result of the counterion substitution with Mg 21 , Ca 21 , and Ba 21 . Nanoindentation studies revealed that the elastic modulus (E) and hardness (H) increase with sulfonation up to a certain level, at which point, the effect of water content further hinders any mechanical reinforcement. The incorporation of counter-ions increases E and H, but the results are dependent upon the size of the counter-ion. DMA results showed that the polymer maintained the glass transition temperature (T g ) of the polyisobutylene (PIB) segment (260 C) regardless of the sulfonation level or counter-ion substituted. However, both the shoulder of the PIB T g (230 C), which was probably caused by a Rouse-type motion, as well as the T g of polystyrene (105 C) disappeared upon sulfonation. Counter-ion substitution increased the storage modulus of the rubbery plateau, which is indicative of a stronger and more thermally stable crosslinked complex formation. Additional unique relaxations were observed with the counter-ions, and could be attributed to the stretching/rotation of the SAO bond and the interaction of the cations with the oxygen in the sulfonic group. FTIR results also revealed a unique shifting of the asymmetric SAO band when counter-ions were added.