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

Abstract

Objectives This study 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. Methods Two nanogels 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. Results Despite 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%. Significance This study 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.

Photocurable bioadhesive based on lactic acid

“…Irgacure ® 2959 was used as the photoinitiating agent since it was proved to be well tolerated over a wide range of cell types and chemical concentrations [25] and has been successfully used in the biomaterials filed by several authors [26][27][28].…”

Controlled nanogel and macrogel structures from self-assembly of a stimuli-responsive amphiphilic block copolymer

“…The initial monomer feed ratio was 7:3 M for DMAEMA and PEGMA indicating PEGMA has a modestly lower reactivity than DMAEMA but the copolymer structure is assumed to be essentially random. The use of the CPBD/AIBN initiating system has previously been demonstrated to promote RAFT polymerization behaviour with the ability to produce block copolymer structures 8 . After the reaction with styrene and AzMSt, the amphiphilic block copolymer was formed confirmed by the appearance of peaks around 6.3 – 7.3 ppm (aromatic protons) in the NMR (Figure 2).…”

Organic Eluates Derived from Intermediate Restorative Dental Materials

“…DMPA is found to induce cell viability [46]. α-Methylstyrene (MS) and cumene (CM) traces could be possibly associated with α-methylstyrene dimer which in turn has served as a reversible addition-fragmentation chain-transfer (RAFT) agent in the synthesis of branched nanogels, containing UDMA crosslinkers, potentially used as shrinkage and stress-limiting resin additives [47]. However, the high temperature conditions during the gas chromatography analysis process can result in the formation of ACP, MS and methyl cumyl ether (MCE) as potential thermal degradation products of cumyl hydroperoxide or dicumyl peroxide [48,49].…”