Atomistic insight into micro-phase separation and gas diffusion in PEO-PBT multiblock copolymers

Atomistic simulation is reported for micro-phase separation and H-2 diffusion in poly(ethylene oxide) (PEO)-poly(butylene terephthalate) (PBT) multiblock copolymers with varying PEO segment length. The simulated densities of copolymers agree well with available experimental data with only 1-2% deviations. A strong interaction exists between PEO segments as evidenced by the sharp peaks in radial distribution functions. With increasing PEO segment length, the fractional free volume marginally increases, PEO and PBT segments tend to be more immiscible and segregated domain size increases. This is consistent with experimental and theoretical studies in the literature. The mobility of PBT segments is almost one order of magnitude smaller than that of PEO segments. With increasing PEO segment length, the mobility of PEO-PBT copolymers is enhanced. For H-2 diffusion in PEO-PBT copolymers, the diffusivity increases with increasing PEO segment length, as experimentally observed. This simulation study provides atomistic insight into the micro-structure and gas transport properties in PEO-PBT copolymers.