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

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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. ***