Spectroscopic Studies on Photophysical and Photochemical Processes in Associated Water-soluble Polymers

已知嵌段共聚物在对其中一种嵌段有选择性的溶剂中形成胶束(聚合物胶束)。由于胶束具有不同于传统洗涤剂胶束的各种性质，人们对其进行了大量的研究。本研究旨在揭示聚合物胶束作为光物理和光化学过程(如能量传递)的反应场的特性。所使用的嵌段共聚物是Pluronic F68(EO_&lt；78&gt；PO_&lt；30&gt；EO_&lt；78&gt；)和Pluronic L64(EO_&lt；13&gt；PO_&lt；30&gt；EO_&lt；13&gt；)。主要研究结果如下：1.研究了罗丹明B(给体)到孔雀石绿(受体)的电子能量转移。胶束的形成大大抑制了能量传递。能量传递的减少归因于胶束化时微粘度的增加主导了浓度效应等其他因素。2.以罗丹明B和十八烷基罗丹明B为荧光探针，研究了Pluronic胶束的结构。结果表明，随着温度的升高，胶束从膨胀到收缩的构象发生了很大的变化，与传统洗涤剂不同，Pluronics的临界胶束浓度(CMC)强烈依赖于温度。根据偏振度和荧光寿命估算了Pluronic胶束的微观粘度。Pluronics的CMC也得到了确定。

Block copolymers has been known to form micelles (polymer micelles) in a solvent selective for one of the blocks. Many investigations have been performed on the micelles because they have a variety of properties different from conventional detergent micelles. This study has been undertaken to reveal the characteristics of polymer micelles as a reaction field for photophysical and photochemical processes such as energy transfer. The block copolymers employed are Pluronic F68 (EO_<78>PO_<30>EO_<78>) and Pluronic L64 (EO_<13>PO_<30>EO_<13>). The results obtained are as follows :1.Electronic energy transfer from rhodamine B (donor) to malachite green (acceptor) are examined. The energy transfer is drastically suppressed as the micelles are formed. The decrease of energy transfer is ascribed to that the increase of microviscosity upon micellization dominates other factors such as concentration effect.2.The structures of Pluronic micelles are investigated by the use of rhodamine B and octadecylrhodamine B as fluorescent probes. It is revealed that the micelles undergo a large conformational change from a swollen to a shrunken structure as temperature is increased and that the critical micelle concentrations (CMC's) of the Pluronics are strongly depend on temperature in contrast to those of conventional detergents. Microviscosities of the Pluronic micelles are estimated from the degree of polarization and the fluorescence lifetimes. The CMC's of the Pluronics are also determined.