Simultaneous Interpenetrating Polymer Networks Based on Poly(2-Oxazoline)s

Interpenetrating polymer networks (IPNs), comprised of two or more independent crosslinked networks in which the individual networks are interlaced, can be used to enhance material properties and increase functionality for applications such as tissue engineering, drug delivery, and biofabrication. IPNs can be formed by either simultaneous or sequential crosslinking, with sequential crosslinking being complicated by the need to infiltrate the constituents of the second network into the first network. Herein, the study reports the first simultaneous IPN based on the cationic ring-opening polymerization (CROP) of 2-methyl-2-oxazoline (MeOx) with bis(butyl-2-oxazoline) (BBOx) crosslinker and the reversible addition-fragmentation chain-transfer (RAFT) polymerization of N,N-dimethylacrylamide (DMAAm) with N,N`-methylene bis(acrylamide) (BAM) crosslinker. Specifically, the compatibility of the synthesis techniques is demonstrated for the preparation of simultaneous IPNs, and it is shown that, by varying the amounts of the two crosslinkers and comparing to single-component networks, the equilibrium degree of swelling (EDS) in water and compressive modulus can be tuned. The results reported demonstrate the utility of CROP and RAFT for preparing IPNs and suggest that with appropriate optimization the technique can be expanded to other monomer pairs which are polymerizable via CROP and RAFT. Cationic ring-opening polymerization of 2-methyl-2-oxazoline and reversible addition-fragmentation chain-transfer polymerization of N,N-dimethylacrylamide are performed simultaneously in a one-pot approach under optimized conditions. This enables the preparation of simultaneous interpenetrating polymer networks (IPNs) with tuneable properties.image