title: Triple-Shape Memory Polymers Based on Self-Complementary Hydrogen Bonding.
abstract: Triple shape memory polymers (TSMPs) are a growing subset of a class of smart materials known as shape memory polymers, which are capable of changing shape and stiffness in response to a stimulus. A TSMP can change shapes twice and can fix two metastable shapes in addition to its permanent shape. In this work, a novel TSMP system comprised of both permanent covalent cross-links and supramolecular hydrogen bonding cross-links has been synthesized via a one-pot method. Triple shape properties arise from the combination of the glass transition of (meth)acrylate copolymers and the dissociation of self-complementary hydrogen bonding moieties, enabling broad and independent control of both glass transition temperature (T(g)) and cross-link density. Specifically, ureidopyrimidone methacrylate and a novel monomer, ureidopyrimidone acrylate, were copolymerized with various alkyl acrylates and bisphenol A ethoxylate diacrylate. Control of T(g) from 0 to 60 °C is demonstrated: concentration of hydrogen bonding moieties is varied from 0 to 40 wt %; concentration of the diacrylate is varied from 0 to 30 wt %. Toughness ranges from 0.06 to 0.14 MPa and is found to peak near 20 wt % of the supramolecular cross-linker. A widely tunable class of amorphous triple-shape memory polymers has been developed and characterized through dynamic and quasi-static thermomechanical testing to gain insights into the dynamics of supramolecular networks.
authors.affiliation: Department of Materials Science and Engineering, The University of Texas at Dallas, 800 West Campbell Road, Mailstop RL 10, Richardson, Texas 75080, United States.
authors.forename: Taylor
authors.initials: T
authors.lastname: Ware
authors.forename: Keith
authors.initials: K
authors.lastname: Hearon
authors.forename: Alexander
authors.initials: A
authors.lastname: Lonnecker
authors.forename: Karen L
authors.initials: KL
authors.lastname: Wooley
authors.forename: Duncan J
authors.initials: DJ
authors.lastname: Maitland
authors.forename: Walter
authors.initials: W
authors.lastname: Voit