Engineering Mechanics of Polymers and Gels through Molecular Design

Stephen Craig, Ph.D., Advisor

Abstract

Covalent polymer mechanochemistry has attracted broad attention in the last decade due to its broad potential in stress-responsive materials. Force-sensitive chemical moieties (mechanophores) embedded into polymer backbones are triggered by mechanical loads, with demonstrated responses that include mechanochromism, small-molecule release, mechano-catalysis, enhancements in material toughness and even electrical conductivity. While many qualitative studies have demonstrated the structure-activity correlation between mechanophore designs and the force-responsive properties of bulk materials, quantitative investigations remain rare. Gaining quantitative perspectives is advantageous for the rational, molecular design of polymer materials with tailored mechanical properties, which ultimately could lead to cost-effective and less wasteful materials.

Here, we probe quantitative structure-activity relationships on three fronts: 1) stereochemical effects in the mechanochemical reactivity of endo- vs. exo- furan-maleimide Diels-Alder adducts; 2) the mechanochemical reaction pathways of dichlorocyclopropane diester ring opening reaction; 3) enhanced mechanics of hydrogels through stress-responsive covalent extension of single strands within the polymer network.