| The free radical polymerization and copolymerization of acrylonitrile (AN)with azobisisobutyronitrile(AIBN)as initiator and methyl acrylate (MA)as comonomer in 1-buty-3-methylimidazolium chloride([bmim]Cl) were investigated for the first time.Acrylic polymers with high molecular weight((?)η＞105),low polydispersity index(PDI＜2.0)and high AN content(mAN＞96 wt%),have been synthesized in[bmim]Cl successfully, which are desirable precursors for carbon fibers.First,the free radical polymerization of AN and MA was carried out. The chemical structures of the resulting polymers were analyzed by Fourier Transform Infrared Spectroscopy(FTIR)and Nuclear Magnetic Resonance(13C-NMR).From the FTIR and 13C-NMR analysis,it is confirmed that the chemical structure of polyacrylonitrile(PAN) synthesized in ionic liquid(IL)was identical with that obtained in conventional solvents.The impact of various factors on the polymerization process,including initiator concentration,monomer concentration,reaction ingredients ratios and temperature were discussed in detail.The reactivity ratios obtained from the Fineman-Ross method were rAN=0.704 and rMA=0.802,which is helpful to control the uniformity of the polymer structure.The apparent activation energy is calculated to be 89kJ/mol,which is similar to the conventional solvents systems.Under the same reaction conditions,the PAN obtained in IL has higher molecular weight((?)η=1.25×105)and lower polydispersity index(PDI=1.84)than that in conventional solvents.From differential scanning calorimetry(DSC)and thermal gravimetric(TG)analysis,it is shown that the copolymer obtained in [bmim]Cl showed a broader exothermic peak and lower initiation temperature,which is helpful to control the cyclization reaction.The obtained polymer gave the higher'char yield'and thermal stability compared to the conventional solvents systems,which is helpful to improve the mechanical properties of carbon fibers.In addition,[bmim]Cl is recycled through vacuum distillation.The recycled IL was reused effectively for more than 4 times without any obvious decline in conversion and molecular weights of the produced polymers.Furthermore,radical polymerization of AN and MA was carried out in a mixture solvent of[bmim]Cl and water for the first time.It is shown that,the polymerization results in water-rich reaction medium (mH2O＞70 wt%)were similar to those in aqueous precipitation system.The effect of the reaction conditions on the polymerization was investigated and the AN/MA copolymers with high molecular weight((?)η＞105)was synthesized successfully. |
PDF Full Text Request