Study On Reaction Kinetics Of Photo-living Radical Polymerization Mediated By The Nitroxide Photosensitized With Thioxanthone

Nitroxide mediated photo-polymerization (NMPP) has attracted considerable interest because of the reaction conditions are mild, and as a novel technique of living polymerization in which control on molecular weight and macromolecular architecture can be achieved.In this paper, a new thioxanthone nitroxide (T-TEMPO) as a photosensitizer were synthesized firstly. Photo-living radical polymerization (PLRP) of isobornyl methacrylate (IBOMA) and methyl methacrylate (MMA) mediated by T-TEMPO have been performed in solution. The reaction kinetics and controlled mechanism of PLRP of IBOMA and MMA in solution were investigated. The PIBOMA-b-PMMA and PMMA-b-P(n-BMA) copolymers were prepared by PLRP in solution, using PIBOMA-T-TEMPO and PMMA-T-TEMPO as a macromolecular initiator respectively. The main work and conclusions as following:1. Using strong sulfuric acid (H2SO4) as a catalyst, a new thioxanthone derivative (TYO) was synthesized by the condensation of bis(2-carboxyphenyl) disulfide (DTSA) with phenoxy-acetic acid at the designed temperature, typically0～4℃. The composition and structure of the product was characterized by melting point, MS, element analysis, FT-IR and1H NMR.2. Using N,N’-dicyclohexyl carbodiimide (DCC) and4-dimethylaminopyridine (DMAP) as a catalyst, a photosensitive mediator (T-TEMPO) was synthesized by the esterification of TYO with4-hydroxy-2,2,6,6-tetramethyl-piperidinyl-l-oxyl(HTEMPO) in methylene dichloride(CH2Cl2). The composition and structure of the product was characterized by melting point, MS, element analysis, FTIR and1H NMR. The spectroscopy performance of the product was investigated by UV-Vis spectrum, fluorescence spectrum and ESR.3. Under optimum experiment conditions, Photo-living radical polymerization of IBOMA and MMA mediated by T-TEMPO have been carried out in solution, using2-methyl-4’-(methylthio)-2-morpholinopropiophenone(Irgacure907) as an initiator. The reaction kinetics and controlled mechanism of PLRP were investigated in detail. The results show that the polymerization is kinetic character of controlled/living radical polymerization, in which the monomer conversion increased linearly with exposure time and the molecular weight increased linearly with the monomer conversion, and the homopolymers exhibite narrow molecular weight distribution (PDI=1.1～1.6). The two kinds of the homopolymers were characterized by GPC, FTIR and1H NMR.4. Poly(isobornyl methacrylate)-block-poly(methyl methacrylate)(PIBOMA-b-PMMA) and poly(methyl methacrylate)-block-poly(n-butyl methacrylate)(PMMA-b-P(n-BMA) diblock copolymers were prepared by PLRP in solution, using PIBOMA-T-TEMPO and PMMA-T-TEMPO as an initiator respectively. The two kind of the diblock copolymers were characterized by GPC,1H NMR, FTIR and TGA.