Concentration dependence of the longest relaxation times of dilute and semi-dilute polymer solutions
Concentration dependence of the longest relaxation times of dilute and semi-dilute polymer solutions
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DOI：
10.1122/1.3160734
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发表时间：
2009-09-01
影响因子：
3.3
通讯作者：
Steinberg, Victor
中科院分区：
文献类型：
--
作者：
Liu, Yonggang;Jun, Yonggun;Steinberg, Victor
通过拉伸单个 DNA 分子的聚合物延伸弛豫和 PAAm 溶液的应力弛豫测量，研究了半柔性 T4 DNA 和柔性 18 M 摩尔质量聚丙烯酰胺 (PAAm) 聚合物溶液在稀和半稀浓度范围内的最长弛豫时间。对于两种聚合物溶液，最长弛豫时间通过相同溶剂粘度 tau/tau(0) 无限稀释时的值归一化，随着浓度的增加而增加。在稀释状态下，随着浓度的增加，最长弛豫时间略有增加，如 tau/tau(0)=[1 + cA - root 2(cA)(1.5) + 2(cA)(2)] 以及 tau/tau(0)=exp(cA) 的经验关系，直到 c 类似于 3c*，其中 A 近似于 0.5eta，其中 c* 是重叠浓度，与理论和先前的一致 实验。对于半稀溶液，tau/tau(0) 随浓度的缩放在两个浓度区域中显示出两个不同的指数，对应于非纠缠和纠缠状态。这些指数与半稀聚合物溶液的动态缩放理论所期望的指数一致。发现从非缠结态到缠结态 c(e) 的交叉浓度与良溶剂中的 9c* 相似，这与基于单分子弛豫、扩散系数和溶液粘度测量的其他实验一致。我们还通过分析文献数据集，测试了在稀释和半稀释状态下，在良好溶剂和 Theta 溶剂中，柔性和半柔性聚合物的最长弛豫时间的浓度依赖性的普遍性。 (C) 2009 年流变学会。 [DOI：10.1122/1.3160734]
The longest relaxation times of polymer Solutions of semi-flexible T4 DNA and flexible 18 M molar mass polyacrylamide (PAAm) in dilute and semi-dilute concentration range are studied by the polymer extension relaxation of stretched single DNA molecules and by the stress relaxation of PAAm solutions measurements. For both polymer solutions, the longest relaxation time normalized by the value at infinite dilution with the same solvent viscosity tau/tau(0) increases with increasing concentration. In the dilute regime, the longest relaxation time increases just slightly with increasing concentration as tau/tau(0)=[1 + cA - root 2(cA)(1.5) + 2(cA)(2)] as well as the empirical relation of tau/tau(0)=exp(cA) up to c similar to 3c* with A approximate to 0.5[eta], where c* is the overlap concentration, in accord with the theory and previous experiments. For the semi-dilute solutions, the scaling of tau/tau(0) with concentration shows two different exponents in two concentration regions, corresponding to the unentangled and entangled regimes. The exponents are consistent with those expected by the theory of dynamical scaling for semi-dilute polymer solutions. The crossover concentration from the unentangled to entangled regime c(e) is found to be similar to 9c* in a good solvent, in accord with other experiments based on the relaxation of a single molecule, the diffusion coefficient, and the solution viscosity measurements. We also test the universality of the concentration dependence of the longest relaxation time for both flexible and semi-flexible polymers in both good and Theta solvents in the dilute and semi-dilute regimes by analyzing literature data sets. (C) 2009 The Society of Rheology. [DOI: 10.1122/1.3160734]