Dynamic Light Scattering Studies on Strong Interaction between Polymer Liquid Crystals and the Gelation Process.

用静态和动态光散射方法研究了聚(γ-α-苄基-α，L-谷氨酸)-甲苯体系的缔合和凝胶化过程。在凝胶(I)的准平衡状态下，在所得到的自相关函数(ACF)中观察到了慢模式，该模式是聚集态PBLG链在各向同性相中的协同自扩散模式。此外，测量的ACF在凝胶化阈值附近进行了振动调制。这种调制的表观频率受热滞和经过时间的影响。事实上，这种调制在大约一天后就减弱了。这一现象可以用浓度波动和预凝胶结构域之间的粘弹性相互作用的叠加来解释。因此，这些事实似乎表明，在这种情况下，凝胶化可能通过成核和生长过程发生(I)。另一方面，根据Cahn理论，实验表明，在凝胶化(II)的猝灭非平衡中，凝胶化是通过调幅分解过程进行的。因此，可以首先在PBLG-甲苯相图中实验测定调幅点温度。随着甲苯溶液浓度的增加，分维增大，关联长度减小，尤其是PBLG凝胶的关联长度小于猝灭后浓度波动的特征最大波长，说明猝灭形成的凝胶结构更致密。

Static and dynamic light scattering measurements have been performed on the association and gelation processes for poly (gamma-benzyl-alpha, L-glutamate) (PBLG) -toluene systems. In the quasi-equilibrium state of gelation (I), the slow mode has been observed in the obtained autocorrelation function (ACF), which was assigned to be a cooperative self-diffusion mode for aggregated PBLG chains in an isotropic phase. In addition, the ACF measured was modulated vibrationally near the gelation threshold. The apparent frequency of this modulation was influenced by thermal hysteresis and the time of elapse. In fact, the modulation was diminished after about one day. This phenomenon could be explained by the superposition of the fluctuation of concentration and the viscoelastic interaction between pre-gel domains. Thus, these facts seem that the gelation may occur by the nucleation and growth process in this case (I). On the other hand, it has become apparent experimentally that the gelation in the quenched non-equilibrium of gelation (II) has proceeded by the spinodal decomposition process, according to the Cahn's theory. As a result, the spinodal temperature could be first determined experimentally in the PBLG-toluene phase diagram. The fractal dimension increased and the correlation length decreased with increasing concentration of toluene solution, and, especially, the correlation length in PBLG gel was shorter than the characteristic maximum wavelength for concentration fluctuation occurred just after quenching, which describes that gel formed by the quenching made a more dense structure.