Synthesis And Characterization Of Side-Chain Polysiloxane Liquid Crystals

A series of liquid crystalline monomers of 4a~4d with different terminal groups wassynthesized via substitution reaction by using 4-(ω-acryloyloxy-ethyloxy)benzoyl chlorideand p-hydroxybenzoic acid, p-methyl phenol, p-hydroxybenzaldehyde, p-cyanophenol as theraw materials. The obtained monomers were characterized by FT-IR and 1H-NMRmeasurements. The liquid crystalline behaviors of these monomers with different terminalgroups were characterized by differential scanning calorimetery (DSC) and polarizing opticalmicroscopy (POM), It was found that different terminal groups had a less effect on the textureof monomers. those monomers of 4a~4d demonstrated the smectic texture, and had a greateffects on melting point, isotropization temperature and mesomorphic range which showed adownward trend. Finally, the compounds of polysiloxanes of 5a~5d were prepared by graftingreaction of those monomers. From the analysis of POM and DSC, the results showed thatliquid crystalline properties were found only for 5a and 5b, they belonged to the smectictexture, their mesomorphic range were from 191.81℃~233.01℃and 188.04℃~249.34℃respectively.New side-chain smectic liquid-crystalline elastomers containing 4-(ω-acryloyloxy-ethyloxy)benzoxy-4'- benzoic acid (M) as smectic mesogenic units and Bis(4-allyloxybenzoxy-4'-butyl benzoate) (N) as smectic crosslinking units were synthesized. The chemical structures ofthe olefinic compounds and obtained polymers were characterized by FT-IR and 1H-NMR.The mesogenic properties were investigated by differential scanning calorimetry (DSC) andpolarizing optical microscopy (POM). The influence of the concentration of the crosslinkingunit on the phase behavior of the elastomers was also studied. The elastomers containing lessthan 8.5 mol% of the crosslinking units revealed elasticity, wider mesophase temperatureranges, and higher thermal stability. The results showed that the glasstransition temperature,and isotropization temperature decreased with an increasing concentation of the crosslinkingunits.