Fabrication and characterization of ionomers and composites based on block copolymers of styrene and isobutylene
The transport properties of poly(styrene-b -isobutylene- b -styrene) were examined as a function of styrene content and morphology. The transport studies included water vapor permeation tests and measuring the diffusion coefficient of liquid water through the block copolymer (BCP) materials by ATR-IR spectroscopy. The chemical environment of the BCPs was then tailored by incorporating ionic groups and a silicate nanophase specifically within the styrene domains of the elastomer materials. The ultimate goal of this research is to examine how incorporating ionic groups and an inorganic phase within targeted phases of the copolymer affect the permselectivity and mechanical properties of the material. Sulfonic acid groups were incorporated into the polystyrene blocks of a BCP (30 mass % styrene) by sulfonation. Some of these materials were then converted to ionomers by neutralizing the acid groups with hydroxide base. The morphology of the self-assembled elastomer ionomers was used as a template for an in-situ sol-gel reaction to incorporate a silicate phase inside the ion-rich styrene regions of the block copolymer ionomers. The morphology of the acid- and ion-form BCPs and composites was characterized by small-angle X-ray scattering and transmission electron microscopy. Dynamic mechanical analysis was used to characterize the thermo-mechanical properties of the materials, which where correlated with the results of the morphology studies. The transport properties of the modified block copolymer materials were analyzed by ATR-IR spectroscopy and the results were explained by simple hydration/water structure models.