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Issue 12, 2012
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Lamellar microdomain orientation and phase transition of polystyrene-b-poly(methyl methacrylate) films by controlled interfacial interactions

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Abstract

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 (XS) 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 XS = 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 XS = 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.

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

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Publication details

The article was received on 03 Dec 2011, accepted on 11 Jan 2012 and first published on 16 Feb 2012


Article type: Paper
DOI: 10.1039/C2SM07297A
Soft Matter, 2012,8, 3463-3469

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

    S. Choi, E. Kim, H. Ahn, S. Naidu, Y. Lee, D. Y. Ryu, C. J. Hawker and T. P. Russell, Soft Matter, 2012, 8, 3463
    DOI: 10.1039/C2SM07297A

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