Studies of Dilute Solution Properties of Oligomers and Polymers

基于螺旋蠕虫链模型，对柔性高分子在较宽分子量范围内（包括低聚物区）的稀溶液性质进行了实验研究。静态性质，例如均方13 EA\：e回转半径、均方光学各向异性、均方电偶极矩和散射函数，是根据光和小角X射线散射和介电测量以及稳态传输系数确定的，即，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）13EA的动态光散射和粘度测量的平移扩散系数和特性粘度：通过比较上述性质对M的依赖性与相应的HW理论预测，检验了模型的有效性，并讨论了高分子链的刚度和局部构象对这些性质的影响。 ...更多信息 关系得到了澄清。在不对称链的情况下，特别注意立体化学组成，即，a-PS和a-PMMA的外消旋二元组分数与M的外消旋二元组分数具有相同的独立性。所有实验结果都可以用相应的HW理论得到很好的解释，说明了模型的有效性.四个基本的HW模型参数已明确确定为上述四种聚合物。根据由此确定的模型参数，可以推导出以下结论。（1）a-PMMA和PDMS链轮廓保留大的螺旋部分。(2)In与通常的概念相反，a-PMMA链比a-PS链更硬。（3）PDMS链比通常认为的更硬。（4）PDMS链在流体力学意义上是很细的.在PDMS的稳态输运系数中存在排水效应，这可以被认为是由上述事实3-（3）和-（4）引起的。由稳态输运系数确定的聚合物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独立于聚合物和s13EA溶剂的普适常数。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