Study on the Coupling of Mutual Diffusion to Viscoelasticity in Polymer Solutions

在本工作中，我们首先证实了在中等浓度的聚合物溶液中相互扩散与粘弹性耦合理论的正确性，从而提供了一种测定扩散系数D、摩擦系数ε、橡胶平台模量L_0、利用动态光散射的自相关函数g ^<（2）>（t）的离散谱分析，结合累积量分析。该方法已成功地应用于某些合成聚合物和“活性”聚合物的溶液，即，聚合物样胶束。主要结果如下：1）对于所研究的所有聚合物溶液，D随浓度c的增加均遵循相同的幂律关系，与聚合物种类、分子量M_ω和溶剂性质无关，表明D随c的变化与溶剂有关。2）L_0值与c^2成正比，并与相应聚合物本体状态下的文献值平滑地联系在一起。结果表明，基于橡胶弹性理论的概念不仅适用于聚合物浓溶液，而且适用于相当稀的聚合物溶液; 3）γ_m与M^<3.4>_ω成正比，与聚合物-溶剂体系无关，符合稳态粘度的3.4次方定律; 4）L_2O_3在环己烷中形成球形胶束，胶束随水的加入而变成圆柱形。在保持卵磷脂分子间距离不变的情况下，圆柱体的长度随水含量的增加而变长。5）表面活性剂C_<12>E_6在水溶液中形成长椭圆形胶束。胶束溶液表现出粘弹性，这是由于在大的c.

In this work, we have, firstly, confirmed the validity the validity of our theory on the coupling of mutual diffusion to viscoelasticity in moderately concentrated polymer solutions, thereby affording a means to determine the diffusion coefficient D, friction coefficient ζ, rubbery plateau modulus L_0, and terminal relaxation time γ_m from the autocorrelation function g^ <(2)>(t) obtained from dynamic light scattering by using the discrete spectrum analysis of g^<(2)> (t) combined with the cumulant analysis. The method has been successively applied to the solutions of some synthetic polymers and also of "living" polymers, i.e., polymer-like micelles. The main results thus obtained are summarized as follows:1) For all the polymer solutions examined, ζ increases with increasing concentration c following the same power-law dependence irrespective of the polymer species, molecular weight M_ω, and solvent quality, indicating that the solvent dependence of D as a function of c is ascribed to that of the osmotic compressibility.2) The L_0 vales sre proportional to c^2 and smoothly connected to the literature values of respective polymers at the bulk state. The results imply that the concept based on the rubber elesticity theory holds not only for polymer concentrates but for rather dilute polymer solutions.3) γ_m is proportional to M^<3.4>_ω irrespective of the polymer-solvent system in good accordance with the 3.4th power-law for the steady-state viscosity.4) Lecithin forms spherical micelles in cyclohexane and the micelles change their shape to the cylindrical with including water. The length of the cylinder is lengthened as the water content is increased, by keeping the distance between lecithin molecules constant.5) The surfactant C_<12>E_6 forms prolate ellipsoidal micelles in aqueous solutions. The micellar solutions exhibit viscoelastic behavior due to network formation by stringlike micelles at large c.