Organic–Inorganic Polycyclooctadienes with Double-Decker Silsesquioxanes in the Main Chains: Synthesis, Self-Healing, and Shape Memory Properties Regulated with Quadruple Hydrogen Bonds
Bingjie Zhao, Honggang Mei, Ning Liu, Sixun Zheng
Abstract
Double-decker silsesquioxane (DDSQ) cages were introduced into the main chains of polycyclooctadiene via a ring-opening metathesis polymerization (ROMP) approach. Toward this end, a macromolecular chain transfer agent for the ROMP was synthesized via acyclic diene metathesis polymerization of 3,13-diallyl DDSQ with the Grubbs second catalyst. To regulate the intermolecular specific interactions, 4-(2-hydroxyethyl)-10-oxa-4-azatricyclo[5.2.1.02,6]dec-8-ene-3,5-dione-2-ureido-4[1H]-pyrimidinone was synthesized and used as a monomer of copolymerization. It was found that the organic–inorganic copolymers were heterogeneous at the nanometer scale. The POSS (viz., DDSQ) cages were aggregated into the POSS nanophases with the size of 20–30 nm. The POSS microdomains behaved as the netpoints of physically cross-linked networks and thus the organic–inorganic copolymers can display the behavior of cross-linked elastomers. As a result of the physical crosslinking, the organic–inorganic copolymers possessed shape memory properties. Meanwhile, the materials possessed excellent self-healing properties and plasticity in solids with the quadruple hydrogen bonds with 2-ureido-4[1H]-pyrimidinone groups. While the organic–inorganic copolymers were used as shape memory materials, their original shapes can be reprogrammed by the use of the plasticity in solids of the materials.