Free Radical Copolymerization Of Acrylonitrile In Ionic Liquid

The free radical polymerization and copolymerization of acrylonitrile (AN) with azobisisobutyronitrile (AIBN) as initiator in 1-buty-3-methylimidazolium chloride ([bmim]Cl) were investigated respectively. The kinetics of polymerization as well as structure, composition and properties of the resulted polymers were investigated.First, the free radical polymerization of AN and IA was carried out. The chemical structure and composition of the copolymers were analyzed by Fourier Transform Infrared Spectroscopy (FTIR) and elemental analysis (CHN). It is shown that the obtained polymers have the same structure and composition with that prepared in conventional solvents. Various reaction factors on the polymerization, including reaction time, initiator concentration, comonomer concentration, monomers concentration and temperature, were discussed in detail. It is found that the copolymerization rate of AN and IA was much higher than that in DMF or DMSO, and the synthesized polymers have high viscosity-average molecular weight and low molecular weight distribution. It is concluded that the proper copolymerization condition for AN and IA copolymerized in [bmim]Cl is as following, initiator concentration was 0.8%, IA concentration was 2%, monomers concentration was 18% and temperature was 67℃.Based on the results of the copolymerization of AN and IA, acrylic acid(AA), acryloamide(AM), monomethyl itaconate(MMIA) and methyl acrylate (MA) were selected as comonomers in the further copolymerization. It is found that all the copolymerization showed high polymerization rate. The obtained copolymers all have lower molecular weight than homopolyacrylonitrile while P(AN-MMIA) has the highest molecular weight of about 1.8×10~5 g/mol and P(AN-AA), P(AN-AM), P(AN-MA) have similar molecular weight of about 1.0×10~5g/mol.The thermal properties of the resulted polymers were analyzed by differential scanning calorimetry (DSC) and thermal gravimetric (TG). It is shown that AM,IA and AA are helpful to the cyclization reaction, but MMIA and MA could retard the cyclization reaction to different extent. The concentration of comonomer also has prominent effect on the thermal properties of the copolymers.At last, the influence of [bmim]Cl on the thermal properties of P(AN-AM) copolymers was quantitatively analyzed. It is found that small amount(<6 wt %) of [bmim]Cl lead to lower initiation temperature of the cyclization and improved the char yield. When [bmim]Cl concentration is 2%, P(AN-AM) gained the highest cyclization degree and char yield, indicating proper amount of [bmim]Cl is good for the thermal property of P(AN-AM).