From equilibrium lamellae to out-of-equilibrium cylinders in triblock copolymer nanolayers obtained via multilayer coextrusion

Abstract

Multilayer coextrusion was used to obtain nanolayered films of self-assembled commercial triblock copolymer poly(methyl methacrylate-b-butyl acrylate-b-methyl methacrylate) (MAM) confined by poly(methyl methacrylate) (PMMA). The MAM layer thickness was varied from 30 nm to 500 nm (i.e. roughly 1 to 15–20 nanodomains) by changing either the number of multiplying elements or the chill roll draw ratio. The as-extruded triblock morphology within the layers was identified as cylindrical using transmission electronic microscopy (TEM) and small-angle X-ray scattering (SAXS). Surprisingly, this differs from the lamellar morphology identified at equilibrium in bulk and thin films for this triblock. Moreover, as the triblock layer thickness is decreased, the triblock morphology is constrained into a preferential orientation. Slightly different packings were observed on films with similar layer thicknesses but achieved with different processing routes. This one-step and industrially scalable method allowing long-range control of the self-assembly is of interest for engineering applications with large quantity of materials needed.