Functionalization of poly(styrene-b-butadiene-b-styrene) via thiol-ene click chemistry for membrane applications

Abstract

The first part of this dissertation focuses on the functionalization of SBS with quaternary ammonium groups for anion exchange membrane in fuel cells. Relevant membrane properties such as hydroxide conductivity, ion exchange capacity, water uptake, and alkaline stability were characterized to evaluate the structure and property relationship of this novel class of ionic block copolymer materials. Morphological characterization of these polymers was also performed utilizing small angle X-ray scattering, transmission electron microscopy, and atomic force microscopy.

The last part of this dissertation describes the selective, “blocky” functionalization of SBS with a thiol in a micelle form to generate “blocky” sulfonate groups along the olefinic middle block and evaluation of this “blocky” functionalization effect on its membrane properties.

The second part of this dissertation studies similar styrene butadiene triblock copolymers but functionalized with heterocyclic amine groups for evaluation as a CO2 selective gas separation membrane. Permeability and selectivity of these membranes for CO2 were measured and compared with other gases including N2, H2, and CH4.

Functional polymers possess a wide range of applications beyond commercial bulk polymers such as poly(ethylene). Among methods for synthesis of functional polymers, post-polymerization modification is one of the most appealing choices. This thesis discusses the use of thiol-ene click chemistry to functionalize the olefinic middle block of poly(styrene-b-butadiene-b-styrene) (SBS) with a variety of functional groups for multiple membrane uses.