RAFT-mediated control of nanogel structure and reactivity: Chemical, physical and mechanical properties of monomer-dispersed nanogel compositions

AbstractObjective tudy examines how nanogel structure correlates with photopolymerization and key polymer properties upon addition of nanogels with latent reactivity into a monomer dispersant to produce polymer/polymer composites. s nogels that retained RAFT functionality based on the synthetic approach were prepared to have different branching densities. These reactive nanogels were dispersed in triethylene glycol dimethacrylate at 0–40 wt%. Reaction kinetics, volumetric shrinkage and shrinkage stress associated with the photopolymerization of nanogel-modified formulations were measured in real time with mechanical properties of the polymers also evaluated. The basic structure of RAFT-derived nanogel particles was examined by the preparation of a separate nanogel constructed with degradable disulfide crosslinking groups. The model nanogel molecular weight and polydispersity were compared before and after degradation. s e the controlled radical synthetic approach, the nanogels, which are composed of multiple interconnected, short primary chains, presented relatively high polydispersity. Through addition of the reactive nanogels to a monomer that both infiltrates and disperses the nanogels, the photopolymerization rate was moderately reduced with the increase of nanogel loading levels. Volumetric shrinkage decreased proportionally with nanogel concentration; however, a greater than proportional reduction of polymerization-induced stress was observed. Mechanical properties, such as flexural strength, storage modulus were maintained at the same levels as the control resin for nanogel systems up to 40 wt%. icance tudy demonstrated that beyond the use of RAFT functionality to produce discrete nano-polymeric structures, the residual chain end groups are important to maintain reactivity and mechanical properties of nanogel-modified resin materials.