Foldamers as Cross-Links for Tuning the Dynamic Mechanical Property of Methacrylate Copolymers

Abstract

This paper reports a foldamer-based approach to modulating the thermal and mechanical properties of cross-linked n-butyl methacrylate copolymers. Intramolecularly hydrogen-bonding-induced folded aromatic amide segments were designed and prepared, which reacted with a salicylaldehyde-bearing prepolymer to form cross-linked copolymers. As a control, analogous aromatic cross-links incapable of forming discrete folded structures due to lack of specific intramolecular H-bonding were also prepared and incorporated into copolymers. From the two series of cross-linked copolymers, 18 films were prepared and characterized by dynamic mechanical analysis (DMA) as well as creep/recovery experiments. We show that, compared to the control, the discrete folded cross-links substantially improve the mechanical properties of the copolymers. We attribute this enhancement to the ability of the folded cross-links to reversibly reveal the hidden length on extension via dissipative cleavage of the intramolecular H-bonds.