Mechanical modification of RAFT-based living polymer networks by photo-growth with crosslinker

Abstract

Abstract In this work we present a study into the usage of crosslinker growth of Reversible addition-fragmentation chain-transfer polymerization (RAFT)-based Living Polymer Networks (LPNs) for the purpose of mechanical strengthening. Previous work with LPNs has thoroughly covered growth with monomers for various goals, and has touched on using a small amount of crosslinker during growth to retain mechanical strength after growth. Herein, we demonstrate growth with both purely crosslinker and purely monomer for the sake of comparison. We also show this across both symmetries of RAFT agent to see how their different growth behaviors affect the results. The asymmetric RAFT underwent a mesh-filling process during growth which resulted in both crosslinker and monomer strengthening the parent network to a similar degree. However, with the symmetric RAFT agent we saw that the crosslinker and monomer growth caused opposite effects due to their impact on the average crosslinking density; while monomer growth lowered it, growth with crosslinker increased it and strengthened the gel accordingly.