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Abstract
This study focused on new visible light-curing (VLC) oligomers exhibiting low shrinkage, low sorption of water, and improved mechanical properties. A family of multi-methacrylates, based on poly(isopropylidenediphenol) resin (BPA), was synthesized, characterized, and evaluated. The commercial BPA resin is prepared from enzymatic polymerization (oligomerization) of bisphenol A. The BPA resin, having an average of eight phenolic hydroxyl groups per molecule, was treated with propylene carbonate and the resultant product, i.e., propoxylated BPA (PBPA) oligomer, was confirmed by Fourier transform infrared spectroscopy (FT-IR) and 13C nuclear magnetic resonance (NMR). The propaxylated BPA (PBPA) was subsequently treated with methacryloyl chloride to produce the multi-methacrylates (EPBPA), identified by FT-IR and NMR. The EPBPA oligomer multi-methacrylate: triethylene glycol dimethacrylate (TEGDMA) (50:50/wt:wt) blends were combined with 0.5 wt% camphorquinone (CQ) and 1.0 wt% N,N-dimethyl-aminoethyl methacrylate (DMAEMA). The control was 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl] propane (BisGMA):TEGDMA (50:50/wt:wt) blends having the same levels of CQ/DMAEMA. Differential photocalorimetry (DPC) and differential scanning calorimetry (DSC) showed these multi-methacrylate/TEGDMA (neat resin) blends have polymerization characteristics comparable to the BisGMA/TEGDMA control. These multifunctional oligomers (EPBPA) have lower polymerization shrinkage and lower uptake of water and some common organic solvents. These results suggest that the new type of polyfunctional methacrylate oligomers (EPBPA) have potential application in formulating dental composites as direct esthetic restorative materials with improved properties.