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Hierarchical Structure in Nanoscale Thin Films of a Poly(styrene-b- methacrylate grafted with POSS) (PS214-b-PMAPOSS27)

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    Hierarchical Structure in Nanoscale Thin Films of a Poly(styrene-b- methacrylate grafted with POSS) (PS214-b-PMAPOSS27)
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    ‡ Department of Chemistry, Pohang Accelerator Laboratory, Division of Advanced Materials Science, Center for Electro-Photo Behaviors in Advanced Molecular Systems, BK School of Molecular Science, and Polymer Research Institute, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea
    § Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1-S8-36 O-okayama, Meguro-ku Tokyo 152-8552, Japan
    ⊥ Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 5376, United States
    *To whom correspondence should be addressed. E-mail: [email protected] (M.R.); [email protected] (T.H.). Telephone: +82-54-279-2120 (M.R.), +81-3-5734-2421 (T.H.).
    †These authors equally contributed to this study
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    Macromolecules

    Cite this: Macromolecules 2010, 43, 24, 10568–10581
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    https://doi.org/10.1021/ma101276d
    Published December 6, 2010
    Copyright © 2010 American Chemical Society
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    Abstract

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    An interesting organic−inorganic diblock copolymer, poly(styrene-b-methacrylate grafted with polyhedral oligomeric silsesquioxane) (PS-b-PMAPOSS), with PS (an average degree of polymerization DP of 214) and PMAPOSS (DP = 27) blocks was prepared: PS214-b-PMAPOSS27. The morphological structures in nanoscale thin films of PS214-b-PMAPOSS27 and their temperature-dependent changes were investigated in detail by performing grazing incidence X-ray scattering (GIXS) with a synchrotron radiation source. GIXS formulas based on structural models were derived for the quantitative analysis of the two-dimensional (2D) scattering data. In addition, the thermal properties of the diblock copolymer were characterized: it was found to be stable up to 330 °C, and to undergo a glass transition at 96 °C (PS block) and a melting transition at 173 °C (PMAPOSS block). The quantitative 2D GIXS analysis found that the diblock copolymer molecules in the thin films undergo phase separation into PS and PMAPOSS domains, which generates a lamellar structure. Surprisingly, in the solvent-annealed films with and without subsequent thermal annealing the lamellar structure is completely oriented in the out-of-plane of the film and is stable up to the degradation temperature. The PMAPOSS layers in the lamellar structure were found to consist of two sublayers, namely a densely ordered layer composed of vertically oriented orthorhombic crystals and a less ordered layer that consists of molecularly stacked layers that are oriented vertically. In both the sublayers, the PMAPOSS block chains have helical conformations and thus are present as molecular cylinders. These molecular cylinders are always oriented in the film plane. On heating, the orthorhombic crystals and the molecularly stacked layers melt over the range 170−190 °C. On subsequent cooling, the orthorhombic crystals and molecularly stacked layers are not fully recovered, which indicates that the formation of orthorhombic crystals and stacked layers in the PMAPOSS domains requires thermal annealing.

    Copyright © 2010 American Chemical Society

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    Macromolecules

    Cite this: Macromolecules 2010, 43, 24, 10568–10581
    Click to copy citationCitation copied!
    https://doi.org/10.1021/ma101276d
    Published December 6, 2010
    Copyright © 2010 American Chemical Society
    Request reuse permissions

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