聚丙烯酸烷基酯侧基差异对链构象性质的影响

EFFECT OF SIDE GROUP DIFFERENCE ON THE CONFORMATIONAL PROPERTIES OF POLY(ALKYL ACRYLATE)S CHAINS

针对聚丙烯酸烷基酯侧基形状、极性的不同,基于高分子链的构象-构型统计理论和生成矩阵方法,推出均方电偶极矩和均方回转半径的改进公式,应用于聚丙烯酸甲酯(PMA)链和聚甲基丙烯酸乙酯(PEMA)链等的链构象依赖性质的研究.得到无规PMA4(4态PMA)和PEMA的偶极矩特征比分别为0.63和0.66,温度系数为-0.66×10-3 K-1和1.72×10-3 K-1,无规PMA和PEMA的均方回转半径的特征比分别为1.73和1.43,温度系数为-1.05×10-3 K-1和-1.28×10-3 K-1,均与实验结果符合.而且考虑链规整程度的不同和酯类基团方向等的改变,PMA和PEMA的特征比也呈现较大的差异,尤其对间同构型链PMA4短链,偶极矩及其温度系数均伴有极大值的出现,这些结果表明聚丙烯酸烷基酯侧基对其链构象性质的影响不能忽略.

Considering the difference of shape and dipole of side groups, the modified formulas of mean-square dipole moment and mean-square radius of gyration of the poly （ alkyl acrylate） s chains were deduced by the conformational-configurational statistic theory and the generator matrix method, and they were used to investigate the eonformational dependent properties of ploy （methyl aerylate） （PMA） and ploy （ethyl methacrylate） （PEMA）. It is found that the eharacteristie ratios of mean-square dipole moment of atactic PMA4 （4-state PMA） and PEMA are respectively 0.63 and 0.66, and their temperature eoefficients are -0.66 ×10^-3K^-1 and 1.72×10^-3K^-1 respectively. The charaeteristic ratios of mean-square radius of gyration of atactic PMA4 and PEMA are 1.73 and 1.43 respectively, and their temperature coefficients are - 1.05 ×10^-3K^-1 and - 1.28 ×10^-3K^-1 respectively. The obtained results are in agreement with the experiment data. Moreover, the differences of ratios between PMA and PEMA from the change of the chain taeticity and the orientation of ester group dipole are obvious. Especially for the short chains of PMA4, there are maxima of both the dipole moment and its temperature coefficient in the syndiotactic configuration. The results display that the effect of side groups on the conformational properties of poly （ alkyl acrylate ） s can not be neglected.