链转移剂单体存在下自由基NaSCN溶液聚合制备支化聚丙烯腈

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

以偶氮二异丁腈(AIBN)为引发剂,醋酸乙烯酯(VAc)为第二单体,甲基丙烯酸-3-巯基丙酰氧基乙酯(MMPOE)为链转移剂单体,45%硫氰酸钠(NaSCN)水溶液为溶剂,进行常规自由基共聚反应合成支化聚丙烯腈(BPAN);研究了链转移剂单体含量对聚合物的影响。通过气相色谱(GC)、核磁共振氢谱(1H-NMR)、三检测凝胶渗透色谱(TD-GPC)、旋转流变仪分别对聚合反应过程和聚合产物进行了表征分析。结果表明:在NaSCN水溶液体系中,以MMPOE为链转移剂单体制得了较高支化程度的支化PAN,其支化程度随MMPOE含量的增加而提高,分子量随MMPOE含量的增加而降低;25℃下,15.7%固体含量的支化PAN溶液的零剪切黏度(η0=3.52 Pa·s)仅为其同分子量的线型聚合物溶液黏度(η0=27.7 Pa·s)的12.7%。

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℃.