Liquid crystalline thermosets 1. Synthesis and characterization of liquid crystalline thermosets' precursor polymers

The synthesis of three novel liquid crystalline monomers and their corresponding linear polymers is described. The chemical structures of the monomers M-1similar toM-3 were confirmed by Fourier transform infrared (FT-IR) and proton nuclear magnetic resonance (H-1 NMR) spectroscopy. Their liquid crystalline properties and phase behavior were studied by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and thermogravimetric analyses (TGA). Monomers M-1similar toM-3 and polymers P-1similar toP-3 all exhibited nematic texture. Moreover, M-3 and P-3 also showed smectic A phase besides nematic phase. Experimental results demonstrated that the melting temperatures, glass transition temperatures, and clearing temperatures of M-1similar toM-3 and P-1similar toP-3 decreased with the spacer length from n = 0 to n = 6. TGA showed that the temperatures at which 5% weight loss occurred were greater than 275 degreesC for P-1similar toP-3.