Thermodynamic Model of Solvent Effects in Semiflexible Diblock and Random Copolymer Assembly

Mao, Shifan; MacPherson, Quinn; Liu, Chunzi; Spakowitz, Andrew J.

doi:10.1021/acs.macromol.8b00172

Title: Thermodynamic Model of Solvent Effects in Semiflexible Diblock and Random Copolymer Assembly

Journal Article · Wed May 23 00:00:00 EDT 2018 · Macromolecules

DOI:https://doi.org/10.1021/acs.macromol.8b00172· OSTI ID:1470934

Mao, Shifan ^[1]; MacPherson, Quinn ^[1]; Liu, Chunzi ^[1];

^[2]

Stanford Univ., Stanford, CA (United States)
Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)

Here, we present a field-theoretic model to predict the equilibrium thermodynamic behavior of semiflexible diblock copolymers and random copolymers in the presence of solvent. We find that in both systems polymer–solvent contacts dramatically influence the thermodynamic behavior with decreasing the copolymer segment length (i.e., molecular weight). When a copolymer has unequal monomer composition, both polymer length and solvent concentration have a strong influence on the phase transition spinodal and magnitude of the critical wave modes. Diblock copolymers exhibit an expanded region of the lamellar phase in the phase diagram with decreasing chain length and polymer concentration. Such effects suggest a breakdown of the dilute approximation for solutions of short diblock copolymers. Random copolymer solutions also exhibit changes in the phase-transition spinodal and critical wave mode at asymmetric chemical compositions. This effect is highly relevant to most random copolymer materials, since a monomer is typically a low-molecular-weight chemical unit.

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