Limitations and Consequences of Conventional and "Living" Radical Polymerizations in the Synthesis of Side-Chain Liquid Crystalline Polymers

9806247 Pugh本研究的目标是合成和表征一系列具有不同分子结构的明确定义的侧链液晶聚合物，以确定具有不同支化类型和支化密度的化学相同的侧链液晶聚合物的混合物是不相容的还是具有有限的相容，从而导致传统自由基聚合合成的侧链液晶聚合物通常表现出广泛的相变。采用原子转移自由基聚合法合成了线型、梳状、超支化、3-、6-和12臂星形聚丙烯酸酯{11-(4‘-氰基苯基-4“-苯氧基)十一烷基丙烯酸酯}S。不同分子结构的相容性及其对相变宽度的影响将通过比较每个分子结构与它们的二元共混物和未混合的复合材料的热致行为来确定。GPC测定的聚合物分子量将与光散射测量和/或MALDI-MS测定的分子量进行比较。星形聚合物的设计使得在聚合后可以裂解臂，以便比较臂的分子量与原始星形聚合物的分子量，并根据其分子量的多分散性来确定臂长度的一致性。不同结构的形状和致密性将通过测定它们的回转半径(光散射)和特性粘度随分子量的变化来研究。尽管在聚合物的溶液和熔体性质方面有大量的实验结果(例如。聚乙烯、聚苯乙烯和聚丁二烯)具有各种明确的分子结构，但没有一种在每个重复单元中涉及具有大侧链的聚合物。因此，SCLCP的合成、溶液和固态表征将极大地扩展我们对聚合物物理化学的理解。这项工作还将提供SCLCP领域唯一的定量动力学数据；将根据Mayo方程和使用代表SCLCPs典型的广泛化学结构的模型链转移剂的标准动力学测量来确定向聚合物的链转移常数。%这项研究是在具有精确控制的分子结构和液晶性能的新型材料领域。***

9806247 Pugh The objective of this proposat is to synthesize and characterize a series of well-defined side-chain liquid crystalline polymers (SCLCPs) with different molecular architectures in order to determine if mixtures of chemically identical SCLCPs with different types of branching and branching densities are either immiscible or have limited miscibitity, and thereby cause the broad phase transitions often exhibited by SCLCPs synthesized by conventional radical polymerizations. Linear, comb, hyperbranched, and 3-, 6- and 12-arm star poly{11- (4'cyanophenyl- 4"-phenoxy)undecyl acrylate}s will be prepared by atom transfer radical polymerization. The miscibility of the different molecular architectures and its effect on the breadth of their phase transitions will be determined by comparing the thermotropic behavior of each of the molecular architectures with that of their binary blends and unmixed composites. The GPC- determined molecular weights of the polymers will be compared with the molecular weights determined by light scattering measurements and/or MALDI-MS. The star polymers are designed so that the arms can be cleaved subsequent to polymerization in order to compare the molecular weight of the arms with that of the original star polymers, and to determine the uniformity of the arm lengths from their polydispersity in molecular weight. The shape and compactness of the different architectures will be studied by determining how their radius of gyration (light scattering) and intrinsic viscosities scale with molecular weight. Atthough there are extensive experimental results on the solution and melt properties of polymers (eg. polyethylene, polystyrene and polybutadiene) with a variety of well-defined molecular architectures, none have involved polymers with a large side-chain in every repeat unit. The synthesis and solution and solid-state characterization of SCLCPs will therefore greatly expand our fundamentat understanding of the physical chem istry of polymers. This work will also provide the only quantitative kinetic data in the field of SCLCPs; chain transfer constants to polymer will be determined from the Mayo equation and standard kinetic measurements using model chain transfer agents representing a broad range of chemical structures typical of SCLCPs. %%% This research is in the area of novel materials with precisely controlled molecular architectures and liquid-crystalline properties. ***