Substrate Interactions Affecting Order-to-Disorder Transition of PS-b-P2VP Films

Abstract

Interfacial interactions keenly affect the transition behaviors as well as controlling the microdomain orientation of block copolymer confined in a film geometry. In this study, we suggest compelling evidence for thickenss-dependent order-to-disorder transitions (ODTs) on polystyrene-b-poly(2-vinylpyridine) (PS-b-PVP) films using ex-situ grazing incidence small angle X-ray scattering measurements. The ODTs of the overlying PS-b-P2VP films are manifested to be two opposing behaviors between preferential and neutral substrates. Below an onset thickness (to) above which the ODT temperature (TODT) of the films are independent of film thickness, TODTs of the lamella- and cylinder-forming PS-b-P2VP films under the effect of preferential substrate remarkably increases as the film thickness is decreased, while the TODT of the PS-b-P2VP films associated with neutral substrate decreases. Numerical calculations based on the discrete chain self-consistent field theory (SCFT) is qualitatively consistent with the experimental results displaying the thickness-dependent (χN)ODT values.