Issue 15, 2017

Self-assembly of gradient copolymers synthesized in semi-batch mode by nitroxide mediated polymerization

Abstract

The effect of diffuse compositional interfaces on copolymer self-assembly was studied via gradient copolymers (GCP). Poly(methyl methacrylate)-grad-(styrene) (PMMA-grad-PSt) copolymers were synthesized in semi-batch mode using nitroxide-mediated polymerization (NMP) with varied monomer injection protocols to produce varied diffuse interfaces (number average molecular weights (Mn) ranged from 62 000 g mol−1 to 94 000 g mol−1 with dispersities (Đ) between 1.35 and 1.59). The GCPs were spun into thin films on substrates made neutral by (St-ran-MMA-ran-hydroxyethyl methacrylate) terpolymers and annealed at elevated temperature to produce vertically oriented microphase-separated domains. The GCPs were found to have domain spacing larger than equivalent monodisperse BCPs, due to their polydisperse nature. This effect was partially offset by the decrease in χ due to the gradient. GCPs synthesized with a single-injection protocol (i.e. less diffuse interfaces) were found to self-assemble into ordered domains. However, GCPs synthesized with long injection times (i.e. more diffuse interfaces) exhibited poor self-assembly attributed to their predicted statistical-copolymer-like middle sequence, which caused a reduction of the effective enthalpic interaction parameter.

Graphical abstract: Self-assembly of gradient copolymers synthesized in semi-batch mode by nitroxide mediated polymerization

Supplementary files

Article information

Article type
Paper
Submitted
16 Dec 2016
Accepted
23 Mar 2017
First published
23 Mar 2017

Soft Matter, 2017,13, 2836-2843

Self-assembly of gradient copolymers synthesized in semi-batch mode by nitroxide mediated polymerization

K. Wylie, I. Bennett and M. Marić, Soft Matter, 2017, 13, 2836 DOI: 10.1039/C6SM02808J

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