Owing to the excellent chemical resistance, impermeability, and mechanical damping of polyisobutylene (PIB), block copolymers containing PIB segments show great performance as barrier elastomer membranes. Via the introduction of a third hydrophilic phase, the moisture transmission capability of these materials can be enhanced. A potential application of a terpolymer with such composition is clothing designed to protect personnel from harmful chemicals and yet allow for the transport of perspiration water for comfort. In prior work, a combination of living carbocationic polymerization (LCP) with atom transfer radical polymerization was used to synthesize linear poly(acrylic acid-b-styrene-b-isobutylene-b-styrene-b-acrylic acid) (PAA-PS-PIB-PS-PAA) pentablock terpolymers, and their morphology as well as physical properties were studied. However, at low PAA contents, the PAA domains of the polymers are constrained within the rigid PS blocks, limiting water transmission and swelling. This resultant morphology is likely due to the better miscibility between PAA with PS rather than PIB. Thus by changing the HB to a polymer with more favorable interactions towards PIB, e.g. poly(ethylene oxide) (PEO), different morphologies could be obtained. In this study, linear PEO-PS-PIB-PS-PEO pentablock terpolymers were synthesized via a combination of LCP and azide/alkyne cycloaddition (CuAAC) "click" reaction technique. PS-PIB-PS (SIBS) core with molecular weight of 35,000 g/mol (with PIB segment of 20,000 g/mol) was first synthesized by LCP of IB followed by sequential addition of styrene. The native sec-benzylic chloride end groups were then substituted with azide groups using NaN3 in a methyl cyclohexane/dimethylformamide cosolvent mixture. Alkyne-terminated PEO with molecular weight of 5,000 g/mol was synthesized by reaction of commercial mono-hydroxyl PEO with propargyl bromide. The PEO blocks were then coupled to the SIBS core using CuAAC technique to give the terpolymer. The morphology and bulk properties of films cast from these materials were investigated.

Structure-property relationships of moisture permeable triphasic polyisobutylene-based thermoplastic elastomers

254th National Meeting (2017)

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