1,2-聚丁二烯分子链的结构和内旋转运动

实验订定了1,2-链节含量分别为8％,30％和90％的1,2-聚丁二烯在30℃甲苯溶液中的Mark-Houwink方程η]=KM~(?)。发现不同样品的α值基本相同,而K值确实随1,2-链节含量的增加而减小,说明溶液中分子链线团变得紧密了。用线膨胀法和Stockmayer-Fixman方程及分子链的统计力学方法,分别得到了样品的玻璃化温度T_g,和它们的分子链内旋转空间位阻因子σ。它们二者符合T_g=A(σ—b),其中A=174(K),b=0.68。反映了1,2-链节对分子链内旋转的阻碍作用。进一步的研究表明,低1,2-链节含量对应着较低的分子链内旋转势垒和内旋转异构化能。

MOLECULAR CHAIN STRUCTURE AND INTERNAL ROTATION OF 1,2-POLYBUTADIENES

The parameters, K and a of η] = KMa/w, for 1,2-polybutadienes at 30℃+ in toluene, has been determined. It has been found that the values of a of samples with various 1, 2-unit contents are basically the same, but the values of K decrease with increase in 1, 2-unit content.The relation between T0 and σ of the samples has been found to be Tg=A(σ-b), in which A and b are 174 and 0.68, respectivly, indicating the internal rotation of the molecular chain is hindered by 1, 2-unit.It has shown that less 1, 2-unit content corresponds to lower potential barrier of internal rotation and hence to lower energy of rotational isomerization.