Nanostructure Scaling in Semi‐Dilute Triblock Copolymer Gels

Abstract

AbstractThere is a considerable body of work that describes the scaling of diblock copolymer micelle dimensions in dilute and semi‐dilute solution based upon block degrees of polymerization and copolymer concentration. However, there is a lack of analogous information for semi‐dilute ABA triblock copolymer gels, which consist of ABA triblock copolymer dissolved in midblock‐selective (B‐selective) solvent. The present study uses small angle X‐ray scattering to extract micelle dimensions for numerous triblock copolymer gels that vary in copolymer identity (and hence block lengths) and copolymer concentration, as well as gels that contain various ratios of two unique triblock copolymers. Analysis of micelle structural data subsequently translates to universal scaling expressions for the micelle core radius – rA ≈ NA0.53NB−0.14ϕABA0.16 where NA and NB are the endblock and midblock degrees of polymerization, respectively, and ϕABA is the volume fraction of triblock copolymer in the gel – and for the intermicelle spacing – lAA ≈ NA0.09NB0.29ϕABA−0.35. Each scaling expression describes the full collection of experimental data very well. Additionally, these scaling expressions are partially in line with expectations from semi‐dilute diblock copolymer solution theory.