Thin films of homopolymers and cylinder-forming diblock copolymers under shear

Arash Nikoubashman, Raleigh L. Davis, Brian T. Michal, Paul M. Chaikin, Richard A. Register, Athanassios Z. Panagiotopoulos

    Research output: Contribution to journalArticle

    Abstract

    We study thin films of homopolymers (PS) and monolayers of cylinder-forming diblock copolymers (PS-PHMA) under shear. To this end, we employed both experiments and computer simulations that correctly take into account hydrodynamic interactions and chain entanglements. Excellent quantitative agreement for static as well as dynamic properties in both the homopolymer and diblock copolymer cases was achieved. In particular, we found that the homopolymer thin films exhibit a distinct shear thinning behavior, which is strongly correlated with the disentanglement and shear alignment of the constituent polymer chains. For the PS-PHMA films, we show that shear can be employed to induce long-range ordering to the spontaneously self-assembled microdomains, which is required for many applications such as the fabrication of nanowire arrays. We found that the impact of chemical incompatibility on the viscosity is only minor in shear-aligned films. Once the domains were aligned, the films exhibited an almost Newtonian response to shear because the cylindrical microdomains acted as guide rails, along which the constituent copolymer chains could simply slide. Furthermore, we developed a model for predicting the onset of shear alignment based on equilibrium dynamics data, and found good agreement with our shear simulations. The employed computational method holds promise for a faster and more cost-effective route for developing custom tailored materials.

    Original languageEnglish (US)
    Pages (from-to)8015-8026
    Number of pages12
    JournalACS nano
    Volume8
    Issue number8
    DOIs
    StatePublished - 2014

    Keywords

    • cylinder-forming diblock copolymers
    • homopolymers
    • shear
    • thin films

    ASJC Scopus subject areas

    • Materials Science(all)
    • Engineering(all)
    • Physics and Astronomy(all)

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  • Cite this

    Nikoubashman, A., Davis, R. L., Michal, B. T., Chaikin, P. M., Register, R. A., & Panagiotopoulos, A. Z. (2014). Thin films of homopolymers and cylinder-forming diblock copolymers under shear. ACS nano, 8(8), 8015-8026. https://doi.org/10.1021/nn502068e