Research On Visible-Light-Induced Radical Polymerization Of Acrylonitrile

In this paper,we successfully built two novel photoinitiating systems at room temperature to synthesize polyacrylonitrile by visible-light-induced atom-transfer radical polymerization and metal-free radical polymerization.The polymerization process is simple,low energy consumption,low operating costs,and environment-friendly.The high conversion,high-molecular-weight with narrow molecular weight distribution of polyacrylonitrile was prepared.The main contents and results are as follows:(1)Polyacrylonitrile(PAN)with high conversion,high-molecular-weight and low dispersity(>90%,Mn.MALLS>8.0×104 g/mol,Mw/Mn<1.30)was synthesized by visiblelight-induced atom transfer radical polymerization(ATRP)at room temperature,which using Ir(ppy)3 as photoredox catalyst and ethyl ?-bromophenylacetate(EBPA)as initiator.The polymerization behaviors was investigated by using Ir(ppy)3 as a catalyst.It was shown that the classic “living” characteristics.Moreover,PAN-b-PBA block copolymer was prepared using macroinitiator PAN-Br with butyl acrylate(BA)polymerization.A possible mechanism of the polymerization was discussed based on the polymerization behaviors and polymer structure.The experiment results suggested this reaction may follow ATRP mechanism.(2)PAN with high-molecular-weight and low dispersity(Mn,MALLS>1.50×105 g/mol,Mn/Mw<1.30)was successfully synthesized by visible-light-induced metal-free radical polymerization at room temperature,which using Eosin Y as photocatalyst and benzenediazonium tetrafluoroborates as initiator.While matrix-assisted laser desorption/ionization time of flight mass spectrometry(MALDI-TOF MS)and 19 FNMR spectroscopy indicated the F-chain-end process.The polymerization behaviors was investigated by using Eosin Y as a catalyst.It was shown that the characteristics behaviour of a steadily increase of the molecular weight with monomer conversion,narrow molecular weight distributions(Mw/Mn<1.30)and linear kinetics.However,the chain extension was failed when using islated produced PAN-F as macro-initiator.The first-order kinetic behavior,molecular weight distributions shifting and "ON/OFF" experiment results suggested this reaction activation/deactivation process may follow the atom-transfer radical polymerization mechanism.(3)The copolymerization of acrylonitrile with five comonomers including itaconic acid(IA),methacrylate(MA),butyl acrylate(BA),styrene(St)and acrylamide(AM)were carried out respectively under visible light irradiation at room temperature by using EosinY as photocatalyst and benzenediazonium tetrafluoroborates as initiator.It was found that using IA as a comonomer could obtain P(AN-co-IA)with high conversion,high-molecular-weight,narrow molecular weight distribution(Conv.>90%,Mn,MALLS>1.70×105 g/mol,Mn/Mw<1.30)and significantly reduce the initiation temperature of the exothere to initiate cyclization at low temperatures.Moreover,differential scanning calorimetry(DSC)curve exhibited a melting peak at approximately 187 ? when the molar ratios of AN/MA of 85/15,which was significantly lower than the decomposed temperature(~315 ?).The polymerization behaviors was investigated at molar ratios of AN/MA of 85/15.It was shown that the characteristics behaviour of a steadily increase of the molecular weight with monomer conversion,narrow molecular weight distributions(Mw/Mn<1.30)and linear kinetics.