(A) study on the morphology of the polystyrene-poly(ethylene oxide) diblock copolymer and polystyrene homopolymer blends at the air/water interface

Abstract

We present the morphology of the polystyrene-poly(ethylene oxide) diblock copolymer (PS-b-PEO) and polystyrene homopolymer (PS homo) blends at the air/water interface. Based on the morphology, we construct a phase diagram using two variables, sum of PS mass in PS-b-PEO and mass of PS homo over total polymer mass, $\phi$, and the ratio of molecular weight (Mn) of PS homo to Mn of PS in PS-b-PEO, $\alpha$. In general, we find out both the increase of domain size and morphology transition from circular to cylindrical to planar morphology as $\phi$ increases, and only the similar morphology transition is seen as α goes up. Although this is observed in a typical morphology of PS-b-PEO as the relative PS block ratio and spreading concentration increase, our blends have two different features: 1) we can adjust the morphology easily by controlling the amount and Mn of PS homo

2) New morphology that we call melt morphology is discovered for small α as PS homo act like plasticizer. In addition, we discuss the suppression of cylindrical morphology of the blends when the absolute size of PS block in PS-b-PEO does not exceed entanglement molecular weight of PS.