The gelation of a hydrophobically modified hyaluronic acid aqueous solution which shows a lower critical solution temperature of about 25 °C was investigated by multi-particle tracking microrheology. The linear viscoelasticity of the gelling system is converted from the microrheological data. The critical gelling temperature T_gel = 36.3 °C was determined from the loss tangent by the Winter–Chambon criterion. The critical exponent n = 0.62 was determined from the shift factors of the time–cure superposition. The length scales of the dynamic heterogeneity of the gelling system were analyzed using a proposed framework where single-particle and multi-particle non-Gaussian parameters were compared. The length scale of the dynamic heterogeneous regions monotonically decreases during the gelation process, consistent with the nucleation-and-growth mechanism of phase separation. Distributions of local viscosity in the gelling system were extracted from the observed distributions of particle displacement as a time-dependent fingerprint of the dynamic heterogeneity of the gelling system. The results and analyzing methods proposed in the present work can be applied to other microrheological studies.

中文翻译：

---

临界溶液温度较低的聚合物溶液在凝胶化过程中的动态异质性

通过多粒子跟踪微流变学研究了疏水改性的透明质酸水溶液的凝胶化，该水溶液的临界溶液温度较低，约为25°C。胶凝体系的线性粘弹性是从微观流变学数据转换而来的。临界胶凝温度T _gel = 36.3°C是根据Winter-Chambon准则由损耗角正切确定的。临界指数n从时间固化叠加的移位因子确定为0.62。使用建议的框架分析了胶凝系统动态异质性的长度尺度，其中比较了单粒子和多粒子非高斯参数。动态异质区的长度尺度在凝胶化过程中单调减小，这与相分离的成核和生长机理一致。从观察到的颗粒位移分布中提取胶凝系统中的局部粘度分布，作为胶凝系统动态异质性随时间变化的指纹。本工作中提出的结果和分析方法可以应用于其他微流变学研究。