Photoinitiated metal-free controlled/living radical polymerization using polynuclear aromatic hydrocarbons

Recently, photoinitiated polymerization has received revitalized interest as it congregates a wide range of economic and ecological anticipations. Because of the excellent advantages, photoinduced polymerization has widely been applied in coatings, adhesives, inks, printing plates, optical waveguides and microelectronics. Theadvantegesofthismethodarehighrateofpolymerizationatambienttemperatures, low energy consumption, solvent-free polymerization, spatial and temporal control over the processes. There currently exist a few methods, where photo induced polymerization can be applied including controlled/living radical polymerizations such as iniferter, nitroxide mediated radical polymerization(NMRP), reversible addition-fragmentation chain transfer polymerizations (RAFT) and atom transfer radical polymerization (ATRP). Among them, ATRP became the most commonly used method as it has higher range of tolerance not only to the initiators but also to various number of monomers. Traditional ATRP requires a low-oxidation state transition metal complex (commonly CuX/L, X = Cl or Br and L = ligand) in conjunction with an appropriate alkyl halide (R-X). The photochemical initiation both enables the easy control of the polymerization under ambient temperature even for heat-sensitive monomers and tends to minimize side reactions like chain transfer or depolymerization. In this thesis, photo-initiated metal-free controlled living radical polymerization of (meth)acrylates, and vinyl monomers was investigated using the polynuclear aromatic compounds,pyreneandanthracene. Fluorescencespectralanalysesalongwithnuclear magneticresonancestudieswereperformedtodeterminetherateconstantsofinitiator radical formation and investigate the mechanisms of polymerization. The obtained polymers were analyzed by spectral and chromatographic methods. Results show that the excited state anthracene undergoes a faster electron transfer reaction with the alkyl halide initiator than the excited state of pyrene. Pyrene excimers, which are formed at higher concentrations, also react with alkyl halides to form initiator radicals. Although pyrene monomers and excimers are acting slower, polymers with higher control over the chain end functionalities and molecular weight characteristics are obtained in comparison to anthracene as sensitizer.