PEO-Based Hybrid Hydrogels with Hairy Nanoparticles as Polyfunctional Crosslinker

Abstract

PEO-Based Hybrid Hydrogels with Hairy Nanoparticles as Polyfunctional Crosslinker

Jessica A. Ellett, Roger A. E. Wright, and Bin Zhao

Department of Chemistry, University of Tennessee, Knoxville, TN 37996

Hydrogels, consisting of a crosslinked 3-dimensional (3D) polymeric network swollen with water, are used in multiple applications such as drug delivery, chemical sensing, and tissue engineering. Synthetic hydrogels, however, tend to be brittle and lack toughness. It has been shown that both high network uniformity and the incorporation of nanoparticles can enhance the mechanical properties of hydrogels. This work is aimed at fabricating hybrid hydrogels with advanced mechanical properties using thiol-terminated polymer brush-grafted silica nanoparticles (hairy nanoparticles) as polyfunctional crosslinker to react with allyl end-functionalized poly(ethylene oxide) (PEO) via “thiol-ene” click chemistry. The first step, the functionalization of chain ends of PEO, is accomplished through a nucleophilic substitution reaction between hydroxyl-terminated PEO and allyl bromide. The hairy nanoparticles are synthesized by surface-initiated reversible addition fragmentation chain transfer (RAFT) polymerization from benzyl dithiobenzoate-functionalized silica nanoparticles, which are prepared by immobilizing a benzyl dithiobenzoate-terminated triethoxysilane onto the surface of silica nanoparticles. After the reduction of the chain ends of polymer brushes to thiol groups, the hairy nanoparticles are used to crosslink allyl-functionalized PEO via “thiol-ene” click chemistry to form a 3D network. By synthesizing these mechanically advanced hydrogels, new research, and thus technology, can begin to develop in many fields.