| Block copolymers offer an additional degree of freedom in tailoring polymer properties. However, relatively few studies have employed these materials in gas permeation studies or evaluated them as membrane materials for water treatment. In this dissertation, the effects of copolymer structure, composition and morphology on transport properties are discussed for two series of fluorinated block copolymers. The underlying motivation is to further the understanding of the structure/property relationships governing transport behavior in this class of materials.; The gas permeabilities of rubbery poly(1,1′-dihydroperfluorooctyl acrylate) (PFOA), glassy poly(1,1′-dihydroperfluorooctyl methacrylate) and poly(styrene)-b-poly(1,1′ -dihydroperfluorooctyl acrylate) copolymers are reported. In general, PFOMA has lower fractional free volume, and based on glass transition temperature, more restricted chain mobility. The PS-b-PFOA copolymers exhibit complex microphase-separated morphologies, and their gas permeabilities are intermediate between those of rubbery PFOA and glassy PS, decreasing in magnitude as PS content increases. Gas permeabilities and selectivities suggest that the PS-b-PFOA morphologies are highly defective laminate structures and are consistent with results from electron microscopy.; Diblock and triblock copolymers consisting of hydrophilic poly(2-dimethylaminoethyl methacrylate) blocks and very low surface energy blocks, PFOMA or poly(1,1,2,2-tetrahydroperfluorooctyl acrylate), have been synthesized by a two-component iniferter technique. Angle-dependent x-ray spectroscopy results and water contact angle measurements indicate that the polymer-air surfaces of the PDMAEMA-b-PFOMA diblock copolymers consist primarily of PFOMA. Transmission electron microscopy reveals that the block copolymers are microphase-separated, exhibiting either cylindrical or layered morphologies that do not change appreciably upon exposure to water. For PDMAEMA-b-PFOMA diblock copolymers, water uptake and water flux increase with increasing PDT content. The PTAN-b-PDMAEMA- bPTAN and PFOMA-b-PDMAEMA-b-PFOMA triblock copolymers have higher and lower values of water uptake, respectively, than anticipated from the PDMAEMA-b-PFOMA diblock data. Accessibility of the hydrophilic PDMAEMA microdomains, as well as morphology and crystallizability of the copolymers, all influence permeation behavior. Salt partition and diffusion coefficients increase monotonically with the amount of freezing water in the hydrophilic microdomains, suggesting that the state of water in the microphase-separated block copolymers is an important factor influencing the salt uptake and transport properties. |
