Characterization of copolymerization of acrylonitrile with the functionalized comonomers in dimethyl sulfoxide solvent and copolymers suitable for carbon fibers
AbstractFree-radical solution copolymerization of acrylonitrile (AN) with four comonomers including itaconic acid (IA), acrylamide (AM), methyl acrylate (MA) and ammonium salt of itaconic acid (AIA) were carried out respectively. Every copolymerization process has been named as AN/IA system, AN/AM system, AN/MA system and AN/AIA system respectively, and the attained polymer is regarded as AN/IA, AN/AM, AN/MA and AN/AIA copolymer respectively. Effect of different comonomers on the polymerization kinetics and viscosity of the spinning drop are discussed in detail. The exothermic reaction of polyacrylonitrile (PAN) precursors is determined by differential scanning calorimetry (DSC), and effect of the different comonomers on the stabilization exotherm properties of PAN precursors were also studied. It has been shown that the rate of polymerization decreases distinctly with an increase of IA content, the ammonium modification can obviously increase the hydrophilicity of copolymer. The falling ball viscosity of AN/IA system is lower when compared with the other three systems, but when under the low concentration of monomer, AN/MA system has the highest viscosity. Electron paramagnetic resonance (EPR) indicates that the peak width change for the different copolymer be mainly caused by the spin-spin interaction. The copolymer of AN/AM has the lowest starting-exothermal reaction temperature and AM can alleviate the exothermic reaction and moderate the stabilization exotherm
Trapping and Electron Paramagnetic Resonance Characterization of the 5′dAdo• Radical in a Radical S-Adenosyl Methionine Enzyme Reaction with a Non-Native Substrate
