Studies on Reaction Kinetics and Structure of Polymer Gels by Photon Correlation Spectroscopy

凝胶中存在冻结(静态)不均匀以及热(动态)浓度波动。我们提出了一种相关的方法来表征和分解这两个贡献，即冻结的不均匀和热涨落。该方法由数百个样品位置的动态光散射测量组成。这被称为系综平均动态光散射(EADLS)。这项工作的另一个亮点是确定凝胶阈值的四种方法。在发生交联的化学反应中，在凝胶阈值出现四个特征：(I)散射强度的突然增加，(Ii)时间-强度关联函数(ICF)中的幂规律行为，(Iii)衰减时间分布函数的特征展宽，以及(Iv)ICF的初始幅度偏离1。对有机化学凝胶、无机硅凝胶和热可逆物理凝胶的有效性进行了检验。我相信，这些工作有望在软物质物理学中开辟一个丰富的领域，作为与连接性相关的聚合物材料的科学。

Frozen (static) inhomogeneities as well as thermal (dynamic) concentration fluctuations are present in gels. We proposed a relevant method to characterize and decompose the two contributions, i.e., the frozen inhomogeneities and thermal fluctuations. This method consists of dynamic light scattering measurements at hundreds of sample positions. This is called the ensemble-average dynamic light scattering (EADLS). Another highlight of this work is the four methods of determining a gelation threshold. During a chemical reaction undergoing cross-linking, four characteristic features appear at the gelation threshold; (i) an abrupt increase in the scattered intensity, (ii) a power-law behavior in the time-intensity correlation function (ICF), (iii) a characteristic broadening of the decay time distribution function, and (iv) a deviation of the initial amplitude of ICF from unity. The validity of these methods was examined for organic chemical gels, inorganic silica gels, and thermoreversible physical gels. I believe that these works promise a rich field in soft matter physics, as the science of connectivity-correlated polymeric materials.