Computational and experimental investigation of morphology in thermoplastic elastomer gels composed of AB/ABA blends in B-selective solvent

Abstract

Thermoplastic elastomer gels (TPEGs) are physically associating gels composed of ABA triblock copolymers that are highly swollen with a B selective solvent. A unique feature of TPEGs, when compared to typical chemically crosslinked gels, is that the properties are dictated by a combination of nano-scale block copolymer morphology and chain level structure. In this paper, we use dissipative particle dynamics (DPD) simulations to examine TPEGs composed of a binary mixture of AB and ABA block copolymers in a B-compatible solvent. The diblock and triblock differ in the block length, where the A and B block of the diblock chains are larger than those of the triblock. The DPD simulations illustrated numerous morphologies of these AB/ABA gels characterized by formation of pure and mixed micelles of various compositions, structures, and sizes. In addition, the ABA/AB copolymer ratio and processing conditions impacted the structural and mechanical properties of these blends. The simulation results were utilized to establish factors that affect an intermicellar distance and bridging chain fraction. The DPD-based morphology predictions were compared with experimental data based on atomic force microscopy (AFM) with good agreement.