水对聚丙烯腈溶液热致变凝胶化的微观促进机理研究

Study on micro promotion mechanism of water on thermotropic gelation of polyacrylonitrile solution

使用分子动力学模拟作为研究方法,从微观层面上研究了聚丙烯腈(PAN)/二甲基亚砜(DMSO)/水(H2O)混合溶液的热致变凝胶化过程,并明确了水的微观促进机理。结果表明,模拟计算得到的含水量为4%(质量分数,下同)的三元体系的凝胶点温度在332.75 K附近,与文献报道的实验结果吻合;水会增加PAN分子链的振动幅度,增加氰基之间发生交联作用的概率,从而促进PAN溶液快速发生凝胶化转变;在一定的范围内,含水量越大,PAN的振动幅度越大;水减少了PAN周围DMSO分子的数量,增强PAN分子链的聚集程度,导致氰基之间更容易发生交联作用。

The thermotropic gelation process of a polyacrylonitrile(PAN)/dimethyl sulfoxide(DMSO)/H2O ternary so-lution system was investigated by molecular dynamics simulation at a microscopic level,and the microscopic promoting mechanism of water on the thermotropic gelation of the ternary solution system was determined.The results indicated that the ternary system with 4 wt%water exhibited a gel point temperature of around 332.75 K through the simulation.This result was consistent with the experimental results reported in literature.Water could increase the vibration ampli-tude of PAN molecular chain and the probability of cross-linking between cyanogen groups,thus promoting the rapid ge-lation of PAN solution.Within a certain range,the vibration amplitude of PAN increased with an increase in the water content.The introduction of water reduced the number of DMSO molecules around PAN and enhanced the aggregation degree of PAN molecular chains,causing a higher cross-linking degree between the cyanogen groups.