Heteroarm Star-Branched Block Copolymers

杂臂星形聚合物含有n个臂，其中x个臂由单体A组成，n-x个臂由单体B组成。这些星形聚合物是具有全新化学结构的有机材料。最近的理论工作预测，它们将表现出不寻常的偏析和相间现象。将开发合成程序，以制备这些具有精确定义的结构的n=3，4的新材料，并在B臂的自由端连接特殊官能团。孤立的异臂恒星中臂间相互作用的结果将根据大环化的速率和平衡来评估，该大环化的速率和平衡是从分子的准分子发射推导出来的，分子中的两个臂在其自由端带有芘。在半稀溶液、熔体和固态中可能发生的各种臂间相互作用之间的区分将通过选择性地标记用于研究准分子发射或非辐射单重态能量转移速率的杂臂恒星来确定。孤立的异臂恒星的动力学，以及它们在浓溶液和熔体中的扩散，将使用脉冲梯度自旋回波核磁共振来确定。

Heteroarm star polymers contain n arms, of which x arms are comprised of monomer A while n-x arms are comprised of monomer B. These star-shaped polymers are organic materials of entirely new chemical structure. Recent theoretical work predicts they will exhibit unusual segregation and interphase phenomena. Synthetic procedures will be developed for preparation of these new materials with n = 3,4 with precisely defined architectures and for the attachment of special functional groups at the free ends of the B arms. The consequences of interarm interactions in isolated heteroarm stars will be assessed from the rates and equilibrium for macrocyclization, as deduced from excimer emission by molecules in which two arms bear pyrene at their free ends. Discrimination among the various types of interarm interactions that can occur in semidilute solution, melts, and in the solid state will be determined with heteroarm stars selectively labelled for study of excimer emission or the rate of nonradiative singlet-energy transfer. The dynamics of isolated heteroarm stars, as well as their diffusion in concentrated solutions and melts, will be determined using pulsed-gradient spin-echo nuclear magnetic resonance.