Institute for Mechanical Process Engineering and Mechanics, Karlsruhe Institute of Technology (KIT) , 76131 Karlsruhe, Germany.
Biomacromolecules. 2013 Oct 14;14(10):3689-96. doi: 10.1021/bm4010436. Epub 2013 Sep 11.
We have investigated the linear viscoelastic properties of high molecular weight hyaluronan in aqueous solution using an experimental approach combining mechanical rheometry and optical microrheology. The complex shear modulus has been measured over a broad frequency range from 10(-1) to 10(7) rad/s. Chain flexibility is characterized by the persistence length lpand this parameter has been determined for the first time in the entangled regime here from high frequency modulus data. At NaHA concentrations above the entanglement concentration ce, lp is essentially independent of polymer concentration, temperature, and ionic strength. The latter is consistent with the Odijk-Skolnick-Fixman theory. The scaling exponent describing the concentration dependence of the plateau modulus G0 agrees well with predictions for polymers in good solvents. The scaling exponents for the specific viscosity ηsp and relaxation time TR are slightly higher than theoretically predicted for polyelectrolytes in the high salt limit, indicating, that molecular aggregation occurs at higher polymer concentrations.
我们使用结合力学流变学和光学微流变学的实验方法研究了高分子量透明质酸在水溶液中的线性粘弹性。在 10(-1) 到 10(7) rad/s 的宽频率范围内测量了复剪切模量。通过测量高频模量数据，首次在缠结区确定了链柔性的特征参数弛豫长度 lp。在高于缠结浓度 ce 的 NaHA 浓度下，lp 基本上与聚合物浓度、温度和离子强度无关。这与 Odijk-Skolnick-Fixman 理论一致。描述平台模量 G0 浓度依赖性的标度指数与在良溶剂中聚合物的预测值吻合得很好。比浓粘度 ηsp 和松弛时间 TR 的标度指数略高于高盐极限下聚电解质的理论预测值，这表明在较高的聚合物浓度下发生了分子聚集。
