Photopolymerizable Liquid Crystal Monomer-Oxide Nanoparticle Composites

Methacrylate and acrylate terminated monomers can be rapidly polymerized to polymer glasses useful in biomaterials, photolithography and rapid prototyping, optical coatings and composites. Unfortunately, polymerization shrinkage results in loss of tolerance and the development of internal stresses which can be especially critical in the case of highly crosslinked glasses. Structurally complicated oligomeric mixes of dimethacrylate monomers that exhibit a nematic liquid crystal to isotropic transition above room temperature have been synthesized in a low cost one pot synthesis to surmount the problem of polymerization shrinkage and the propensity of single component monomers to crystallize from the liquid state. Photopolymerization from the ordered liquid crystal state into a less ordered glass minimizes volumetric shrinkages to between 1–2% at greater than 90% polymerization conversion. These polymer glasses exhibited elastic bending moduli of 1.2 GPa to 1.5GPa, fracture strengths of 70–100MPa and fracture toughness of K=0.3–0.4 (MPa)^1/2. In some cases the glasses exhibited ductile behavior which is unusual for highly crosslinked materials. Room temperature viscosities of 100P–2000P permit facile processing of the liquid crystal monomers with inorganic particles to make dental restorative composites.