DIFFUSION OF DEXTRAN IN AQUEOUS (HYDROXYPROPYL)CELLULOSE
DIFFUSION OF DEXTRAN IN AQUEOUS (HYDROXYPROPYL)CELLULOSE
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DOI：
10.1021/ma00083a017
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发表时间：
1994-02-28
期刊：
影响因子：
5.5
通讯作者：
RUSSO, PS
中科院分区：
文献类型：
--
作者：
BU, Z;RUSSO, PS
采用荧光光漂白法（FPR）测定了8种不同分子量标记右旋糖酐在半刚性聚合物（羟丙基）纤维素（HPC）水溶液中的探针自扩散系数D(s)。加上游离染料和单个染料标记的聚合物乳胶，探针的水动力半径R(h)为5-551埃。对于右旋糖酐，D(s)对M的依赖性使D(s)近似于M(- β)， β在水中几乎等于1/2。在最浓的HPC溶液中，β几乎等于1。小型探测器显示出与斯托克斯-爱因斯坦关系的强烈偏差。随着探针尺寸的增加，影响不那么严重。大部分扩散数据符合Langevin-Rondelez方程，D(s)/D0 = eta0/eta + exp[-(R(h)/xi)delta]，其中D0和eta0分别为纯溶剂中的扩散系数和粘度，xi为相关长度，delta为参数。对于稀溶液中的小探针，Langevin-Rondelez关系存在例外（R(h)/xi < 0.1）。数据还使用Phillies提出的流体动力学缩放模型和Johansson及其同事开发的圆柱形细胞模型进行解释。研究了HPC基质分子量对不同尺寸探针扩散的影响；小探针对基质分子量相对不敏感，但大探针的扩散确实依赖于HPC的分子量。讨论了FPR的分析应用。HPC根据分子量有选择性地阻滞右旋糖酐，其作用随HPC浓度的增加而增强。两种分子量不同的右旋糖酐混合物的FPR信号在HPC溶液中呈明显的双指数关系，即使它不是纯水。聚合物基质对恢复时间分布的扩展表明，聚合物基质中的FPR可以作为一种中等分辨率的方法来检测大分子的多分散性，在精神上类似于分析凝胶电泳，但适用于未带电的聚合物，适当标记。初步的评估是有希望的。
Fluorescence photobleaching recovery (FPR) was used to measure the probe self-diffusion coefficients, D(s), of eight labeled dextrans with different molecular weights in aqueous solutions of the semirigid polymer (hydroxypropyl)cellulose (HPC). With added measurements of free dye and a single dye-labeled polymeric latex, the probe hydrodynamic radius, R(h), spanned 5-551 angstrom. For dextrans, the dependence of D(s) upon M obeys D(s) approximately M(-beta) with beta almost-equal-to 1/2 in water. In the most concentrated HPC solution studied, beta almost-equal-to 1. Small probes show strong deviations from the Stokes-Einstein relation. The effect was less severe as probe size increased. Most of the diffusion data fit the Langevin-Rondelez equation, D(s)/D0 = eta0/eta + exp[-(R(h)/xi)delta], where D0 and eta0 are respectively the diffusion coefficient in and viscosity of pure solvent, xi is the correlation length, and delta a parameter. Exceptions to the Langevin-Rondelez relation were found for small probes in dilute solution (R(h)/xi < 0.1). The data are also interpreted using the hydrodynamic scaling model advanced by Phillies and a cylindrical cell model developed by Johansson and co-workers. The effect of the molecular weight of the HPC matrix upon the diffusion of variously sized probes was also studied; small probes were relatively insensitive to matrix molecular weight, but the diffusion of larger probes did depend on the molecular weight of the HPC. Analytical applications of FPR are considered. HPC selectively retards dextrans according to molecular weight, the effect becoming stronger as HPC concentration is increased. The FPR signal for a mixture of two dextrans with different molecular weights can be markedly biexponential in HPC solution, even if it is not pure water. This expansion of the recovery time distribution by the polymer matrix suggests that FPR in a polymer matrix can serve as a medium-resolution method to detect macromolecular polydispersity, similar in spirit to analytical gel electrophoresis but applicable to uncharged polymers, suitably labeled. A preliminary evaluation is promising.