Exploration of Dynamic Structure-Process-Property Relationships in Vitrimer-Like Materials and Multimodal Polymer-Clay Composites

Abstract

When designing and modeling composite materials, it is common to make simplifying assumptions regarding intermolecular interactions so that the composite can be considered as a homogeneous material with predictable behavior. This approach is acceptable for traditional composite processing and in any case where the components of the composite have uniform, static structures after they are incorporated into the bulk material; however, real materials for engineering applications rarely fit these idealized models and the components have specific, non-negligible interactions and transient topologies. This body of work examines two such materials: vitrimeric thermoplastic polymers and polymers reinforced with layered aluminosilicates; specifically, we 1) attempt to deconvolute contributions of bond exchange kinetics and segmental relaxation in a covalent adaptive network comprised of a poly(methyl-methacrylate)-poly(hydroxy-ethyl-methacrylate) copolymer (PMMA-PHEMA) crosslinked with dynamic aromatic disulfide bonds and 2) examine the role of in-situ dehydration on intercalation and exfoliation of montmorillonite agglomerates into nanoplatelets during melt-extrusion of a polyethylene terephthalate glycol (PETG)-montmorillonite-zeolite composite. In both studies, we challenge the fundamental assumptions used to simplify kinetic, thermodynamic, and transport properties of the material and utilize bulk rheological measurements to extrapolate mechanistic understandings of the material behavior that can be exploited in process design to yield desirable properties and morphologies in the end-use material.