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

[9806247] Pugh本论文的目的是合成并表征一系列具有不同分子结构的定义良好的侧链液晶聚合物（SCLCPs），以确定具有不同类型分支和分支密度的化学相同的sccps混合物是否具有不混溶性或有限的混溶性。从而导致常规自由基聚合合成的sclcp所表现出的广泛相变。将通过原子转移自由基聚合法制备线性、梳状、超支化和3、6和12臂星形聚{11-（4‘氰苯- 4’ -苯氧基）十一烷基丙烯酸酯}。不同分子结构的混相性及其对相变宽度的影响将通过将每种分子结构的热致性与其二元共混物和未混合复合材料的热致性进行比较来确定。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。设计的星型聚合物在聚合后可以进行旋臂切割，以便将旋臂的分子量与原星型聚合物的分子量进行比较，并通过其分子量的多分散性来确定旋臂长度的均匀性。通过确定它们的旋转半径（光散射）和固有粘度与分子量的比例，将研究不同结构的形状和紧凑性。虽然有大量的实验结果对聚合物的溶液和熔体的性质(如。聚乙烯，聚苯乙烯和聚丁二烯)具有各种明确定义的分子结构，没有一个涉及在每个重复单元中都有大侧链的聚合物。因此，SCLCPs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基本理解。这项工作也将为SCLCPs领域提供唯一的定量动力学数据；链转移常数将从梅奥方程和标准动力学测量中确定，使用模型链转移剂代表了sclcp典型的广泛化学结构。这项研究是在具有精确控制的分子结构和液晶特性的新型材料领域。＊＊＊

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. ***