Development Of Novel Photoinduced"Living"/Controlled Radical Polymerization System

Photochemistry has been widely used in not only conventional radical polymerization,like coating, adhesive, micro-electronic and so on, but also almost each specific method ofLRPs to overcome the problems encountered in known LRP methods.The majormotivation to utilize photochemistry is to enable LRP to proceed under moderate thermalconditions by activating the dormant species at low temperature. Furthermore, the LRP’ssystem can be achieved simply. Other attractive advantages are the reduction of metalcatalyst loading in ATRP, and increased fidelity of the apolymer-end structure inDT-mediated LRPs. Since these advantages of photoirradiation can be achieved withlow-power, readily available light sources, the use of photo-LRP inindustrial-scalesynthesis should be feasible. The results are as follows:(1). Well-controlled poly(vinyl acetate)(PVAc) was successfully synthesized byphoto-induced cobalt-mediated radical polymerization using (2,4,6-trimethylbenzoyl)diphenylphosphine oxide (TPO), which is commercially available, cheap, easy to store andhas a high initiation efficiency, as the initiator in the presence of Co(acac)2under UVirradiation (65μW/cm2at365nm) at30℃. The polymerization showed characteristics ofliving polymerization behaviors, such as linear kinetics, the molecular weight of thepolymers linearly increasing with conversion, and the obtained polymers had a narrowmolecular weight distribution. The polymerization can reach high conversions with acontrolled manner (>80%, polymers with a molecular weight distribution in the range of1.1–1.4) after a short induction time. Polymers with molecular weights as high as120000gmol-1, with a narrow molecular weight distribution, were obtained. The mechanism of thepolymerization was proposed based on the polymerization behavior and polymer structure.(2). Well-controlled poly(methyl methacrylate) was synthesized by themediating of dimanganese decacarbonyl [Mn2(CO)10]/2-cyanoprop-2-yl1-dithionaphthalate (CPDN) with photo-induced controlled radical polymerizationof methyl methacrylate under visible light (green LED with λmaxof565nm) or sunlight irradiation at moderate temperature. The manganese carbonyl [Mn2(CO)10]was acted as the light absorbing component, and2-cyanoprop-2-yl1-dithionaphthalate (CPDN) was acted as pseudo-alkyl halide initiator andmediating agent. The polymerization showed the characteristics behaviour of livingpolymerization, such as linear kinetics, the molecular weight of the polymerslinearly increasing with monomer conversion, and the obtained polymers showednarrow molecular weight distribution, under the appropriate conditions. Theobtained polymer showed high end functionality degree, which could be used forfurther chain extensions, using either through traditional thermal initiated RAFTpolymerization or through light-irradiated LRP in the presence of [Mn2(CO)10]. Thepossibility of stopping and restarting the polymerization process was realizedsimply by turning off or on the LED light.