Lamellar microdomain orientation and phase transition of polystyrene-b-poly(methyl methacrylate) films by controlled interfacial interactions

Seunghoon Choi, Eunhye Kim, Hyungju Ahn, Sudhakar Naidu, Yonghoon Lee, Du Yeol Ryu, Craig J. Hawker, Thomas P. Russell

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The orientation of lamellar microdomains and phase transition for the thin films of a symmetric polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) on random copolymer-grafted substrates were investigated by transmission electron microscopy (TEM) and grazing-incidence small-angle X-ray scattering (GISAXS). The styrene mole fraction (X S) in random copolymers of P(S-r-MMA) was controlled to tune the interfacial interactions at the substrates from PS-selective to PMMA-selective. Except in the case of a neutral substrate with X S = 0.55, all the films showed the parallel orientations of lamellar microdomains, which were validated by the TEM images. However, the GISAXS analysis of PS-b-PMMA films indicated that the intensity ratio of the out-of-plane scattering to the in-plane scattering can be a sensitive indicator for evaluating the degree of orientation of lamellar microdomains or surface neutrality at the substrates. The orientation of lamellar microdomains on a neutral substrate was influenced by the film thickness and molecular weight of PS-b-PMMA, which results from predominantly the entropic contribution to the free energy in competition between the chain-end effect and nematic term. Intriguingly, the order-to-disorder temperature (ODT) of PS-b-PMMA films on a series of the substrates shows a minimum at X S = 0.55. The ODT measurements, a new approach to evaluating the interfacial interactions at substrates, confirm that a neutral substrate induces surface compatibility between the PS and PMMA blocks at the substrate.

Original languageEnglish
Pages (from-to)3463-3469
Number of pages7
JournalSoft Matter
Issue number12
Publication statusPublished - 2012 Mar 28


All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Condensed Matter Physics

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