title: Construction of monomer-free, highly crosslinked, water-compatible polymers.
abstract: Polymeric dental adhesives require the formation of densely crosslinked network structures to best ensure mechanical strength and durability in clinical service. Monomeric precursors to these materials typically consist of mixtures of hydrophilic and hydrophobic components that potentially undergo phase separation in the presence of low concentrations of water, which is detrimental to material performance and has motivated significant investigation into formulations that reduce this effect. We have investigated an approach to network formation based on nanogels that are dispersed in inert solvent and directly polymerized into crosslinked polymers. Monomers of various hydrophilic or hydrophobic characteristics were copolymerized into particulate nanogels bearing internal and external polymerizable functionality. Nanogel dispersions were stable at high concentrations in acetone or, with some exceptions, in water and produced networks with a wide range of mechanical properties. Networks formed rapidly upon light activation and reached high conversion with extremely low volumetric shrinkage. Prepolymerizing monomers into reactive nanostructures significantly changes how hydrophobic materials respond to water compared with networks obtained from polymerizations involving free monomer. The modulus of fully hydrated networks formed solely from nanogels was shown to equal or exceed the modulus in the dry state for networks based on nanogels containing a hydrophobic dimethacrylate and hydrophilic monomethacrylate, a result that was not observed in a hydroxyethyl methacrylate (HEMA) homopolymer or in networks formed from nanogels copolymerized with HEMA. These results highlight the unique approach to network development from nanoscale precursors and properties that have direct implications in functional dental materials.
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO, USA.
authors.forename: E A
authors.initials: EA
authors.lastname: Dailing
authors.affiliation: Department of Craniofacial Biology, School of Dental Medicine, University of Colorado, Aurora, CO, USA.
authors.forename: S H
authors.initials: SH
authors.lastname: Lewis
authors.affiliation: Department of Craniofacial Biology, School of Dental Medicine, University of Colorado, Aurora, CO, USA.
authors.forename: M D
authors.initials: MD
authors.lastname: Barros
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO, USA Department of Craniofacial Biology, School of Dental Medicine, University of Colorado, Aurora, CO, USA Jeffrey.Stansbury@ucdenver.edu.
authors.forename: J W
authors.initials: JW
authors.lastname: Stansbury
mesh_terms: D000096:Acetone / Q000737:chemistry; D001672:Biocompatible Materials / Q000138:chemical synthesis / Q000737:chemistry; D002074:Butanones / Q000737:chemistry; D003764:Dental Materials / Q000138:chemical synthesis* / Q000737:chemistry; D055119:Elastic Modulus; D005782:Gels; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D017953:Isocyanates / Q000737:chemistry; D008422:Materials Testing; D008623:Mercaptoethanol / Q000737:chemistry; D008689:Methacrylates / Q000138:chemical synthesis / Q000737:chemistry; D049329:Nanostructures / Q000737:chemistry*; D009570:Nitriles / Q000737:chemistry; D018583:Pliability; D011092:Polyethylene Glycols / Q000737:chemistry; D058105:Polymerization; D011108:Polymers / Q000138:chemical synthesis* / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: D001672:Biocompatible Materials; D002074:Butanones; D003764:Dental Materials; D005782:Gels; D017953:Isocyanates; D008689:Methacrylates; D009570:Nitriles; D011108:Polymers; D011109:Polymethacrylic Acids; D014867:Water; C098758:tetraethyleneglycol dimethacrylate; D000096:Acetone; C041979:2,2-bis-(4-(2-methacryloxyethoxy)phenyl)propane; D011092:Polyethylene Glycols; D008623:Mercaptoethanol; C005044:hydroxyethyl methacrylate; C005222:methylethyl ketone; C029845:2-isocyanatoethyl methacrylate; C004526:azobis(isobutyronitrile)
keywords: adhesive resin; hydrophilic; nanogel; phase separation; photopolymerization; polymer networks