Synthesis and characterization of multi-ionic block copolymers and blended membranes for chemical protective clothing applications

This study discusses the synthesis of sulfonated amine block copolymers and the effect of multiple ionic domains and counter-ion substitution on polymeric membranes' morphology and transport properties for chemical protective clothing (CPC) applications. The monomers 2-(tert-butylamino) ethyl methacrylate, 2-ethoxy ethyl methacrylate, and styrene were used to prepare the block copolymers by atom transfer radical polymerization (ATRP). The copolymers were then sulfonated by chemical grafting with pendants sulfobutyl groups onto the polymer structure. Properties of the resulting membranes were evaluated as a function of block composition, incorporation of sulfonic groups, and counter-ion substitution. Blended membranes with sulfonated poly(styreneisobutylene-styrene) (SIBS) were also studied. A series of materials characterization techniques (e.g., Fourier-transform infrared spectroscopy [FT-IR], thermogravimetric analysis [TGA], atomic force microscopy [AFM], Small-angle X-ray scattering [SAXS]/wide-angle X-ray scattering [WAXS]) were performed to describe the changes to the membranes. The results indicate that synthesized copolymers lack phase segregation mainly because of a low sulfonation on the central amine block, leading the material to have a low Water/ DMMP selectivity. As the sulfonated copolymers were blended with SIBS 75, the breathability of the membranes were enhanced 1.5 times, and almost all candidates achieved the water vapor transport rate limit of 1500 g m(-2) day(-1). Finally, the better-found candidates for DMMP CPC were Mg2+ membranes, achieving selectivity between 20 and 90 range.