Effects of Grafting Density on Block Polymer Self-Assembly: From Linear to Bottlebrush

ORAL

Abstract

Grafting density is an important structural parameter that impacts the physical properties of architecturally complex polymers. The physical consequences of varying the grafting density (z) were studied in the context of block polymer self-assembly. Well-defined block polymers spanning the linear, comb, and bottlebrush regimes (0 ≤ z ≤ 1) were prepared via grafting-through ring-opening-metathesis polymerization (ROMP). Small-angle X-ray scattering (SAXS) experiments demonstrate that these graft block polymers self-assemble into long-range-ordered lamellar structures. For seventeen series of block polymers with variable z, the scaling of the lamellar period with the total backbone degree of polymerization (d* ~ Nbbα) was studied. The scaling exponent α monotonically decreases with decreasing z and exhibits an apparent transition at z ≈ 0.2, suggesting significant changes in the backbone and side chain conformations. A model is proposed in which the characteristic ratio (C∞), a proxy for the backbone stiffness, scales with Nbb as a function of the grafting density: C∞ ~ Nbbf(z). Understanding the scaling behavior provides valuable insight into conformational changes with grafting density, thereby introducing new opportunities for block polymer and materials design.

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Presenters

  • Alice Chang

    Division of Chemistry and Chemical Engineering, California Institute of Technology, California Institute of Technology, Chemistry, California Institute of Technology, 2. Division of Chemistry and Chemical Engineering, California Institute of Technology

Authors

  • Alice Chang

    Division of Chemistry and Chemical Engineering, California Institute of Technology, California Institute of Technology, Chemistry, California Institute of Technology, 2. Division of Chemistry and Chemical Engineering, California Institute of Technology

  • Tzu-Pin Lin

    Division of Chemistry and Chemical Engineering, California Institute of Technology, California Institute of Technology, Chemistry, California Institute of Technology

  • Byeongdu Lee

    X-ray Science Division, Argonne Natl Lab, Advanced Photon Source, Argonne National Laboratory, Argonne National Laboratory, X-ray Science Division, Argonne National Laboratory

  • Robert Grubbs

    Division of Chemistry and Chemical Engineering, California Institute of Technology, California Institute of Technology, Chemistry, California Institute of Technology, 2. Division of Chemistry and Chemical Engineering, California Institute of Technology