Heteroarm Star-Branched Copolymers

该基金由材料研究部的聚合物项目和化学部的有机合成项目共同资助。含有单体A的x臂和单体B的n-x臂的异臂星形聚合物应该表现出不寻常的偏析和相间现象。活性连接反应将用于合成由聚苯乙烯和聚二烯臂组成的A2B2星形聚合物，并将使用一种新的通用荧光标记化学方法在臂末端连接芘、蒽和萘基团。一系列具有明确结构的异臂星型共聚物将用于探索其在固态，熔体和溶液中的独特动态和平衡特性。孤立异臂星臂间相互作用的后果将从大环化的速率和平衡来评估，从分子的准分子发射推断，其中两个臂在其自由端带有芘或萘基团。在半稀溶液、熔体和固态中可能发生的各种类型的臂间相互作用之间的区分将通过选择性标记的异臂星来确定，用于研究准分子发射或福斯特转移速率。孤立异臂星的动力学及其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。

This grant is jointly funded by the Polymer Program in the Division of Materials Research and the Organic Synthesis Program in the Division of Chemistry. Heteroarm star polymers containing x arms of monomer A and n-x arms of monomer B should exhibit unusual segregation and interphase phenomena. Living linking reactions will be used to synthesize A2B2 star polymers composed of polystyrene and polydiene arms, and a new general fluorescent-labeling chemistry will be utilized to attach pyrene, anthracene, and naphthalene groups at the termini of the arms. A series of heteroarm star copolymers with well-defined structures will be used to explore their unique dynamic and equilibrium properties in the solid state, in the melt, and in solution. 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 or naphthalene groups at their free ends. Discrimination between 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 labeled for the study of excimer emission or the rate of Forster transfer. The dynamics of isolated heteroarm stars, and their diffusion in concentrated solutions and melts, will be determined using pulsed-gradient spin-echo NMR.