Order−Disorder and Order−Order Transitions in Mixtures of Highly Asymmetric Triblock Copolymer and Low Molecular Weight Homopolymers

Abstract

The order−disorder and order−order transitions (ODT and OOT) of a series of mixtures of a compositionally asymmetric polystyrene-block-polyisoprene-block-polystyrene copolymer (SIS) (fPS = 0.131) and low molecular weight PS homopolymers with different molecular weights have been investigated by using transmission electron microscopy (TEM), synchrotron small-angle X-ray scattering (SAXS), and rheology. ODT temperatures determined from the discontinuous change in 1/Imax and σq2 vs 1/T plots were found to be in reasonable proximity to the ones determined from the discontinuous change in log G‘ vs T plots. Various OOT's were also identified for a few of V4113/PS mixtures, as evidenced from both SAXS and rheology. This was further confirmed by TEM for the quenched samples. Spherical microdomains in liquidlike packing (LLP) observed for pure V4113 at low temperature were found not to be an equilibrium phase, which would transform completely to spheres in body-centered-cubic array (BCC) with prolonged annealing ...