Issue 1, 2016

Reordering transitions during annealing of block copolymer cylinder phases

Abstract

While equilibrium block-copolymer morphologies are dictated by energy-minimization effects, the semi-ordered states observed experimentally often depend on the details of ordering pathways and kinetics. Here, we explore reordering transitions in thin films of block-copolymer cylinder-forming polystyrene-block-poly(methyl methacrylate). We observe several transient states as films order towards horizontally-aligned cylinders. In particular, there is an early-stage reorganization from randomly-packed cylinders into hexagonally-packed vertically-aligned cylinders; followed by a reorientation transition from vertical to horizontal cylinder states. These transitions are thermally activated. The growth of horizontal grains within an otherwise vertical morphology proceeds anisotropically, resulting in anisotropic grains in the final horizontal state. The size, shape, and anisotropy of grains are influenced by ordering history; for instance, faster heating rates reduce grain anisotropy. These results help elucidate aspects of pathway-dependent ordering in block-copolymer thin films.

Graphical abstract: Reordering transitions during annealing of block copolymer cylinder phases

Supplementary files

Article information

Article type
Paper
Submitted
30 Sep 2015
Accepted
02 Oct 2015
First published
06 Oct 2015

Soft Matter, 2016,12, 281-294

Reordering transitions during annealing of block copolymer cylinder phases

P. W. Majewski and K. G. Yager, Soft Matter, 2016, 12, 281 DOI: 10.1039/C5SM02441B

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