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.

Photopolymerizable nanogels as macromolecular precursors to covalently crosslinked water-based networks

“…Solution free radical polymerization produced particles with molecular weight in the 30–150 kDa range and radius <10 nm while avoiding macrogelation. The MH-α values are significantly reduced compared to typical values for a linear polymer and correspond well to previous reports on the GPC analysis of nanogels and hyperbranched polymers 25,31,32 .…”

Combined, independent small molecule release and shape memory via nanogel-coated thiourethane polymer networks

“…We have previously demonstrated that nanogels can be efficiently functionalized with methacrylate groups via an alcohol-isocyanate click reaction and directly polymerized into crosslinked networks in the absence of small monomer 42,43 . Previous reports have further detailed the formation of covalently conjugated nanogel-based coatings on functionalized surfaces using a variety of click reactions including alkyne-azide, thiol-alkyne, and Michael addition reactions 44,45 .…”

“…Nanogels were synthesized as previously described (see supporting information and 42 ). Polyfluor 570 was included at 0.1 wt% to yield fluorescently tagged nanogels.…”

Advances of nanomaterial applications in oral and maxillofacial tissue regeneration and disease treatment

“…Nanomaterials are also efficient in reducing the friction of archwire. For instance, nanocoating materials made of Ni‐P and fullerene‐like nanoparticles of WS 2 or Co and fullerene‐like WS 2 nanoparticles (Dailing, Lewis, Barros, & Stansbury, 2014), nitrogen‐doped TiO 2 nanoparticles or Ag‐Zr nanocomposite coatings have shown both the friction reduction and corrosion resistance of the archwire. However, there are also limitations present, as the dissolve of nanoparticles from brackets may impair enamel esthetics, and thus affect the patient satisfaction after clinical treatment.…”