LIQUID-CRYSTALLINE BISPROPARGYL THERMOSETS

A series of rigid-rod bispropargyl thermoset monomers have been synthe sized. These monomers were examined by differential scanning calorimet ry (DSC) and hot stage polarized optical microscopy. Enantiotropic or monotropic nematic liquid crystalline phases were observed for all but two monomers. Partial curing of these reactive liquid crystalline mon omers resulted in the formation of stable liquid crystalline phases wi th broad nematic phase ranges. In one example, a monomer that was neit her enantiotropic nor monotropic exhibited a stable nematic phase afte r partial curing. DSC investigations indicated that the onset temperat ure of thermally induced cross-linking was approximately 260 degrees C and insensitive to the phase type. The rate of cure was insensitive t o the phase in which the cure occurred due to the unusual reaction mec hanism for the propargyl end group.