Wavelength tunability in photoinitiated cationic polymerization
Onium salts, widely used cationic photoinitiators, have absorption in the short wavelength of the UV spectrum. However, their spectral sensitivity can be tuned up to the visible region by using several methods. Photosensitization of onium salts, their charge transfer complex formation and their free radical promotion are some techniques that are used to provide wavelength flexibility. This chapter summarizes these methods. Upon irradiation photosensitizers such as anthracene, perylene and phenothiazine form exciplexes with onium salts generating reactive species via electron transfer. Furthermore, ground state charge transfer formation Correspondence/Reprint request: Dr. Y. Yagci, Istanbul Technical University, Department of Chemistry, Maslak, Istanbul 34469, Turkey. E-mail: yusuf@itu.edu.tr
Influence of N-vynilcarbazole on the photopolymerization process and properties of epoxy-acrylate interpenetrating polymer networks
Abstract Photocured simultaneous epoxy-acrylate interpenetrating polymer networks (IPNs) were formed both under irradiation by UV-lamp and natural sunlight. The conversion degrees of functional groups were calculated by using data obtained from Fourier transform infrared (FTIR) spectroscopy. The influence of N-vynilcarbazole (NVC) as a photosensitizer on the kinetics of IPN photopolymerization was investigated. The conversion degrees of epoxy groups were revealed to increase significantly with the addition of NVC to the given systems. The phase morphology of IPNs was analyzed by optical and scanning electronic microscopy as well as by dynamic mechanical analysis (DMA). The data obtained using DMA method, which was used for analyzing the IPN samples with different component ratios, indicate the formation of both phase-separated and single-phase IPNs. The phase separation is occurred only in NVC-containing 50:50 IPN.
Interaction parameters in mixtures of polystyrene−poly(methyl methacrylate)−toluene
Abstract Polymer-polymer interaction parameters in the system polystyrene-poly(methyl methacrylate)-toluene have been calculated. The magnitudes of these parameters indicate that polymer-polymer interaction is enhanced among smaller molecules but hindered when the polymer concentration is increased.