Method: An amphiphilic nanogel was prepared by polymerization of ethoxylated bisphenol-A-dimethacrylate with ethoxylated hydroxyethyl methacrylate in the presence of mercaptoethanol. To complete the reactive nanogel synthesis, isocyanatoethyl methacrylate was added to a fraction of the available hydroxyl groups. The nanogel was readily dispersible in water at either 10 or 50 wt% and with an added water soluble initiator, these transparent solutions were photopolymerized with reaction kinetics monitored by near-infrared. The nanogel was also dispersed in HEMA at the same concentrations and photocured with the wet compressive modulus determined relative to the HEMA homopolymer control.
Result: The 50 wt% nanogel dispersed in water produced a flexible photopolymer construct (98% conversion) that remained clear upon water evaporation, which indicates a dense, continuous network. The 10 wt% nanogel solution failed to produce any three-dimensional structure and exhibited limited conversion (26%), as expected for spatially isolated particles. The wet modulus of the HEMA control was 5±3 MPa compared with either 22±8 or 28±6 MPa for the 10 and 50 wt% nanogel-modified HEMA samples, respectively.
Conclusion: Water dispersible nanogels can contribute to or even solely generate relatively strong, water-equilibrated polymer networks whether formed dry or in the presence of water. This nano-materials approach appears well suited to the application of dental adhesives.
Keywords: Biomaterials, Polymerization and Polymers
See more of: Dental Materials 6: Polymer-based Materials-Chemistry and Composition