Studies of the Excluded-Volume Effects and Chain Conformations of Oligomers and Polymers in Dilute Solutions.

本文研究了固定立体化学组成的无规聚苯乙烯(外消旋二元组分f_r=0.59)、无规聚甲基丙烯酸甲酯(f_r=0.79)和链端固定结构的聚异丁烯在较宽的相对分子质量范围内对稀溶液性质的排除体积效应。所得结果总结如下：1)对于回转半径展开因子α_S，准双参数方案是有效的，即α_S可以仅表示为Yamakawa-Stockmayr-Shimada理论中定义的尺度排除体积参数*的函数，该理论在螺旋蠕虫链的基础上考虑了排除体积和链刚度的影响。由于链的刚性，传统的双参数理论不适用于α_S。链刚度的影响仍然很大：对于M&GT；10^6.2)准双参数方案对…也是有效的粘性半径膨胀系数较大，如在α_S的情况下。即使对于M&gt；10^6，链刚性对α_a也有很大的影响。如果在特性黏度中没有观察到排出效应，则在水平分圆中不会出现这种影响。在温度3)，出现在第二维里系数A_2中的穿透函数psi不仅仅是α_S的函数，这表明常规和准双参数方案都不适用于psi。PSI分别取决于M和ON13EA：由于链的刚性而排除的体积强度。Psi的实验结果可用考虑链刚性对A_2影响的Yamakawa理论半定量地解释。对于小M，链末端对A_2的影响在Theta和良好溶剂中都是显著的。这种影响是不能忽略的，即使对于相对较大的M，直到约10^5。观察到的A_2的M依赖关系由考虑到对A_2的这种影响的Yamakawa 13EA理论定量地表示。

In this work, we have studied the excluded-volume effects on dilute solution properties of atactic polystirene with fixed stereochemical composition (the fraction of racemic diads f_r=0.59), atactic poly(methyl methacrylate) with f_r=0.79, and pol13EA\ : yisobutylene with fixed structure of chain ends over a wide range of molecular weight M from oligomers and polymers. The obtained findings are summarized as follows :1)A quasi-two-parameter scheme is valid for the gyration-radius expansion factor alpha_s. That is, alpha_s may be expressed as a function only of the scaled excluded-volume parameter * defined in the Yamakawa-Stockmayr-Shimada theory that takes a13EA\ : ccount of the effects of excluded-volume and chain stiffness on the basis of the helical wormlike (HW) chain. The conventional two-parameter theory does not hold for alpha_s because of chain stiffness. The effect of chain stiffness remains large ev13EA\ : en for M > 10^6.2)The quasi-two-parameter scheme is also valid for th … More e viscosity-radius expansion factor alpha_<eta> as in the case of alpha_s. The effect of chain stiffness on alpha_<eta> also remains large even for M > 10^6. The draining effect does not appear in13EA\ : alpha_<eta>, if it is not observed in the intrinsic viscosity [eta]_<(〕SY.horizontally divided circle.〔)> at THETA.3)The interpenetration function psi appearing in the second virial coefficient A_2 is not a function only of alpha_s, indicating that neither the conventional- nor the quasi-two-parameter scheme is valid for psi. psi depends separately on M and on13EA\ : the excluded-volume strength because of chain stiffness. The experimental results for psi are semi-quantitatively explained by the Yamakawa theory that takes account of the effect of chain stiffness on A_2.4)For small M, the effect of chain ends on A_2 is significant in both THETA and good solvents. The effect cannot be neglected even for relatively large M up to ca. 10^5. The observed M dependence of A_2 is quantitatively expressed by the Yamakawa13EA\ : theory that takes account of that effect on A_2. Less