Interference light-induced photogeneration of metal nanoparticle in polymer films was explored. The nanoparticle was obtained from metal complex homogeneously dispersed in the film. Standing waves resulting from light interference were generated by irradiating nearly monochromatic light to the sample placed on a reflective substrate. During irradiation metal nanoparticles were developed by photoreduction of the metal complexes forming layers rich with particles. These nanoparticle-enriched layers were found to align in parallel to the reflective substrate, and they were separated from each other by a constant spacing. This layer spacing was varied by changing the wavelength and/or the incident angle of the irradiating light. The observed results show that the spatial distribution of the nanoparticles is determined by the optical interference within the film. Surprisingly, regions exist between the nanoparticle-enriched layers where the metal species are not detected. Such regions extends for distances larger than tens of nanometers. This means that the metal complexes initially homogeneously dispersed within the polymer were transported away from certain regions upon photoirradiation. The metal precursors are preferentially photoreduced into the metal nanoparticles at the constructive interference regions. The spatially varying consumption rates of the precursors are considered to lead a concentration gradient, thereby causing a directional diffusion of the unreduced precursors toward the regions where constructive interference occurs.
The thermal properties of bis-GMA-based resins containing a synthesized crystalline DME-TDC which was dissolved to bis-GMA/'FEGDMA base resin by 10 or 20wt% were examined. Camphorquinone (0.5%) and a reducing agent (0.5%) were added to the base resin before the addition of DME-TDC. A thermoanalytical study using differential thermal analysis (DTA) and differential scanning calorimetry (DSC) showed that thermal change in the DTA and DSC curves depended on the composition of the bis-GMA-based resins. Heat for curing was lowest in 50/50 base resin of 40wt% bis-GMA/60wt% TEGDMA, 50/50 and 60/40 base resins in DTA analysis during heating. The addition of DME-TDC to each resin increased heat requirements in 50/50 resin and decreased heat requirements in 40/60 and 60/40 resins. The thermal decomposition of 50/50 bis-GMA-based resin including DME-TDC occurred at a higher temperature than that in 40/60 and 60/40 based resin. The value of activation energy for curing performance was lowest for a DME-TDC including bis-GMAbased resin.
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