Miscible Blends of a Thermotropic Liquid Crystalline Polymer and Sulfonated Polystyrene Ionomers
The miscibility of a wholly aromatic thermotropic liquid crystalline polyester (LCP), Vectra® A, with lightly sulfonated polystyrene ionomers (SPS) was assessed. Blends were prepared by melt mixing in an intensive mixer. The sulfonation level and the choice of the cation used to neutralize the ionomer influenced miscibility. Zinc salts of an SPS with 5.3 mol% sulfonation were miscible at all compositions with the LCP, but lithium salts with the same sulfonation level formed two phases, a pure LCP phase and an ionomer-rich mixed phase. Zinc salts of an ionomer with 10.8 mol% sulfonation were also miscible with the LCP when the blend was richer in the ionomer, but two-phase blends were obtained for LCP-rich compositions. FTIR analyses failed to identify a specific intermolecular interaction between the ionomers and the LCP. That and the fact that increasing sulfonation did not improve miscibility of the zinc salt ionomers with the LCP led to the conclusion that miscibility in this system arose from intramolecular repulsive interactions along the ionomer chain. The addition of 5.3Zn-SPS to the LCP lowered the tensile modulus, the ultimate strength and the ultimate elongation.