Department of Chemistry and Macromolecular Studies Group, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
J Phys Chem B. 2010 Apr 15;114(14):4777-82. doi: 10.1021/jp9121886.
The optical tracer self-diffusion of rodlike poly(benzyl-alpha,l-glutamate) (PBLG) is measured in pyridine solutions spanning the isotropic-liquid crystalline phase boundary for two different molecular weights, M = 134 500 (contour length L = 921 A, axial ratio x = 58) and M = 24 600 (L = 168 A, x = 10.5). The results are compared to previously published data for PBLG with M = 232 000 (L = 1590 A, x = 99). Under the conditions of the measurements, the two longer rodlike polymers align in the liquid crystalline phase with their cholesteric screw axis in the vertical direction. The diffusion is measured in a particular direction normal to this over distances that are long compared to the polymer lengths. Except for the shortest polymer, whose cholesteric screw axis does not assume the vertical alignment, the diffusion suddenly increases as the liquid crystalline phase is entered, then declines, signaling the disappearance of topological constraints in the isotropic phase having a vertical component. The solutions also contain a small, fluorescent component whose mobility was not at all affected by the isotropic-liquid crystalline phase transition.
棒状聚（苄基-α，L-谷氨酸）（PBLG）的光学示踪自扩散在跨越各向同性-液晶相边界的吡啶溶液中进行，针对两种不同的分子量 M = 134500（轮廓长度 L = 921Å，轴比 x = 58）和 M = 24600（L = 168Å，x = 10.5）进行了测量。将结果与先前发表的 M = 232000（L = 1590Å，x = 99）的 PBLG 的数据进行了比较。在测量条件下，两个较长的棒状聚合物在液晶相中以其胆甾相螺旋轴垂直排列的方式排列。扩散在垂直于该方向的特定方向上进行，距离远远长于聚合物的长度。除了最短的聚合物外，其胆甾相螺旋轴没有采用垂直对齐的方式，随着进入液晶相，扩散突然增加，然后下降，表明在具有垂直分量的各向同性相中拓扑约束的消失。这些溶液还包含一个较小的荧光成分，其流动性完全不受各向同性-液晶相转变的影响。
