Synthesis of mesogenic and oligo polyols and their influence on polyurethane properties
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Synthesis and properties of various novel polyurethanes (PUs) and poly(urethane ureas) (PUUs) were investigated. The formation of PU prepolymer in bulk was investigated via in and ex situ Infrared spectroscopy to obtain rate constants for various diisocyanates reacting with poly(tetramethylene oxide) (PTMO). PUUs were prepared from PTMO and a modified polyether containing methyl side groups. The introduction of methyl side groups into the polyether reduced the crystallinity of the PUUs and increased both flexibility and phase separation. Several attempts were made to prepare liquid crystalline PUs via mesogenic diols. Via differential scanning calorimetry and polarised optical microscopy the crystallinity and melting temperature of these PUs were found to increase with increasing rigidity of the mesogenic diol. The nature of the hydrogen bonding, as observed by Infrared spectroscopy, was primarily dependent on the nature of the diisocyanate. Through a combination of two diisocyanates with a mesogenic diol a new enantiotropic liquid crystalline PU was successfully prepared. The synthesis of poly(lactic acid) oligomers was optimised to improve their suitability as a precursor for PUs. Quality of the oligomers, in terms of MW and end group control, could be improved through polycondensation in solvent with molecular sieves or via solid state polymerisation.