Preparation of Branched Polyacrylonitrile via Free Radical Polymerization in NaSCN Solution with a Chain Transfer Monomer

Branched polyacrylonitrile(BPAN) was prepared by traditional radical polymerization in the presence of 2-(3-mercaptopropionyloxy)ethyl methacrylate(MMPOE) as the chain transfer monomer. Vinyl acetate(VAc) was introduced as the second monomer, and the polymerization was initiated using 2,2'-azobisisobutyronitrile(AIBN) and carried out in 45% NaSCN solution. The influence of chain transfer monomer dosage on the copolymerization was investigated. Gas chromatography(GC), proton nuclear magnetic resonance(1H-NMR), triple-detection gel-permeation chromatography(TD-GPC), and rotation rheometer were used to determine the monomer conversion, molecular weight and viscosity of the resulted branched polymer. The results show that, PAN with high degree of branching was prepared and the degree of branching increases when the dosage of MMPOE increases, while the molecular weight decreases gradually with the increase of MMPOE dosage because of chain transfer reaction. The zero-shear viscosity of branched PAN solution with 15.7% solid content is only 12.7% of their linear counterpart with the same molecular weight at 25℃.