Studies of Dilute Solution Properties of Oligomers and Polymers

在螺旋蠕虫链模型的基础上，对包括低聚物区在内的大范围分子量M范围内柔性聚合物的稀溶液性质进行了实验研究。通过光和小角X射线散射和介电测量，确定了无规聚苯乙烯(a-PS)、无规聚甲基丙烯酸甲酯(a-PMMA)、聚异丁烯和聚二甲基硅氧烷(PDMS)的稳态输运系数，即平移扩散系数和特性黏度，并测定了它们的静态性质，如均方回转半径、均方光学各向异性、均方电偶极矩和散射函数。通过比较上述性质对M的依赖关系和相应的HW理论预测，检验了模型的有效性以及高分子链的刚性和局部构象对适当的…的影响更多的联系被澄清。特别注意了不对称链的立体化学组成，即a-PS和a-PMMA，并证实了每种聚合物样品的外消旋二聚体的分数与M的指数相同。所有的实验结果都可以用相应的HW理论很好地解释，表明了该模型的有效性。对于上述四种聚合物中的每一种，都明确确定了四个基本HW模型参数。根据所确定的模型参数，可以得出以下结论。(1)α-PMMA和PDMS链轮廓保留了很大的螺旋部分。(2)与通常的概念相反，a-PMMA链比a-PS cha13EA\：In更硬。(3)PDMS链比通常认为的要坚硬。(4)在流体力学意义上，PDMS链很细。在PDMS的稳态输运系数中存在排水效应，这可以认为是由上述事实3-(3)和-(4)引起的。由稳态输运系数确定的高分子链的流体动力学线性尺寸与由均方回转半径确定的静态线性尺寸之比不是一个与聚合物和溶剂无关的普适常数。较少

On the basis of the helical wormlike (HW) chain model, an experimental study was made of dilute solution properties of flexible polymers over a wide range of molecular weight M, including the oligomer region. Static properties such as the mean-squar13EA\ : e radius of gyratio, mean-square optical anisotropy, mean-square electric dipole moment, and scattering function were determined from light and small angle X-ray scattering and dielectric measurements, and steady-state transport coefficients, i.e., the translational diffusion coefficient and intrinsic viscosity from dynamic light scattering and viscosity measurements for atactic polystirene (a-PS), atactic poly(methyl methacrylate) (a-PMMA), polyisobutylene, and poly(dimethylsiloxane) (PDMS)13EA\ : . From comparisons of the dependences of the above properties on M with the respective HW theoretical predictions, the validity of the model was examined and effects of the stiffness and local conformation of polymer chains on those proper … More ties were clarified. A special care was taken of the stereochemical composition in the case of the asymmetric chains, i.e., a-PS and a-PMMA, and the values of the fraction of racemic diads of the samples for each polymer were confirmed to be the same indepe13EA\ : ndent of M.The main results obtained in this study are as follows.1. All the present experimental results may be well explained by the corresponding HW theories, indicating the validity of the model.2. The four basic HW model parameters have been determined unambiguously for each of the above four polymers.3. On the basis of the model parameters thus determined, the following conclusions may be deduced. (1)The a-PMMA and PDMS chain contours retain large helical portions. (2)In contrast to the usual notion, the a-PMMA chain is stiffer than the a-PS cha13EA\ : in. (3)The PDMS chain is stiffer than usually considered. (4)The PDMS chain is very thin in the hydrodynamic sense.4. The draining effect exists in the steady-state transport coefficients of PDMS, which may be regarded as arising from the facts 3-(3) and -(4) above.5. The ratio of the hydrodynamic linear dimension of polymer chains determined from the steady-state transport coefficients to the static one determined from the mean-square radius of gyration is not a universal constant independent of polymer and s13EA\ : olvent. Less