Nuclear Seminar - RNDr. Katarína Cifraničová (30.4.2025)
Wednesday 30.4.2025 at 14:00, Lecture room F1/364
RNDr. Katarína Cifraničová (Department of Nuclear Chemistry Faculty of Natural Sciences CU):
Photopolymerization of dimethacrylates studied by positron annihilation spectroscopy
Abstract:
Dimethacrylate-based photopolymers are highly cross-linked polymer networks that are essential in applications requiring rapid polymerization, such as light-curable materials for dental medicine. Mixtures of D3MA and UDMA monomers in various ratios, including the literature recommended 1:1 ratio as well as experimental ratios of 4:1, 2:1, 1:2, and 1:4, were polymerized using near-UV light in the presence of a photoinitiator. The microstructural properties of these materials were analyzed by positron annihilation photoelectron spectroscopy (PALS) to determine the ortho-positronium lifetime and the corresponding local free volume. The double bond conversion was monitored by near-infrared spectroscopy (NIR), the bulk density by Archimedes' law and the glass transition temperatures by dynamic mechanical thermal analysis (DMTA). It was found that decreasing the thickness and increasing the amount of photoinitiator leads to a more pronounced free volume gradation, which can significantly affect the resulting material properties, including density and double bond conversion. Based on the combination of the observed parameters, the suitability of the different monomer ratios for use in dental applications was evaluated.