较高等规度丙烯腈成纤聚合物的合成

以无水氯化镁为添加剂,考察了不同条件下的丙烯腈聚合反应,研究了溶剂种类、聚合温度和氯化镁与丙烯腈的摩尔配比对聚合反应及聚合物等规度的影响,并确定了最佳反应条件,正己烷为溶剂,偶氮二异丁腈(AIBN)为引发剂,聚合温度为60℃,氯化镁与丙烯腈的摩尔比为2∶1.在此条件下,研究了单体浓度和引发剂浓度对丙烯腈(AN)均聚合、丙烯腈/衣康酸(AN/IA)二元共聚合和丙烯腈/衣康酸/丙烯酸甲酯(AN/IA/MA)三元共聚合反应的影响,并获得了较高等规度(三单元组全同分数30.2%～55.9%)的丙烯腈均聚物和共聚物.不同等规度的丙烯腈聚合物的热分析(DSC及TGA)表明,随着聚合物等规度的提高,聚合物的环化放热峰值温度向高温区移动,而且随着聚合物等规度的提高,环化放热峰变宽.随着聚合物等规度的提高,聚合物的热稳定性变差,热失重增加,碳收率降低.

SYNTHSIS OF HIGHLY ISOTACTIC POLYACRYLONITRILE

Acrylonitrile(AN) homopolymerization and the copolymerization were examined under various conditions in the presence of anhydrous magnesium chloride(MgCl2).The polymers were obtained with high isotacticity.The effect of solvents,reaction temperature,the molar ratio of MgCl2 and AN on AN homopolymerization and the copolymerization and the tacticity of the polymers were investigated.The optimum reactive conditions to obtain the polymers with high isotacticity are as follows:hexane as the solvent,2,2′-azobisisobutyronitrile(AIBN) as the initiator,the temperature of 60℃ and the molar ratio(MgCl2/AN) of 2∶1.The effects of monomer concentration and initiator concentration on the AN homopolymerization,AN/IA(itaconic acid) copolymerization,AN/IA/MA(methylacrylate) copolymerization were investigated.The homopolymers and copolymers with highly triad isotactic content(30.2%～55.9%) have been obtained.The polymers were characterized by 13C-NMR and Fourier transform infrared(FTIR) spectra.At the same time,the thermal properties of the polymers were characterized by differential scanning calorimetry(DSC) and thermogravimetry analysis(TGA).The DSC results show that the exothermic peak temperature of the copolymers increases with the degree of isotacticity,as well as the exothermic peaks of copolymers become wider.The TGA results reveal the copolymer with high isotacticity shows rapid weight loss when the temperature is higher than approximately 300℃,the char-yields and thermal stability of the copolymers are decreased with the increasing of the degree of isotacticity.