The Effect of Polymer Architecture on Glass Formation and Mechanical Properties

Advances in polymer synthesis have triggered tremendous growth in the development of materials with highly customizable properties. One approach to alter the properties of polymer-based materials is to alter the architecture of the constituent polymers. Therefore, we perform a comprehensive structural and dynamical analysis of several polymer architectures: rings, chains, and stars. Increasing the number of arms of star polymers, we find that the structure and dynamics approach those of soft spheres. We also consider a more unusual architecture, mechanically interlocked polymers, a unique class of macromolecules wherein polymer components are linked by one (or more) sliding chains. These novel linkages may lead to new materials with unique stimulus-response and fatigue-resistant properties. Since these polymer materials are relatively new, no molecular model exists at present. Accordingly, we develop and parametrize a model for star mechanical polymers being synthesized by Professor Brian Northrop's lab in the Chemistry Department. Using this model, we predict that certain properties, such as the glass transition temperature and yield stress, differ from conventional polymers. However, the main factor contributing to these differences does not appear to be chain sliding, but rather the bulkiness of mechanical linkages.