Synthesis and properties of side-chain cholesteric liquid crystalline elastomers containing tetra-vinyl crosslinking units

The synthesis of side-chain cholesteric liquid crystalline elastomers containing crosslinking agent pentaerythriol tetra-p-allyloxybenzoate (M-1) and mesogenic monomer 4-cholesteryl-4'-undecenyloyloxybenzoate (M-2) is presented by hydrosilication reaction. The chemical structures of the monomers and liquid crystalline networks were confirmed by Fourier transform infrared (FT-IR) and proton nuclear magnetic resonance (H-1 NMR) spectroscopy. Mesomorphic properties and phase behavior were investigated by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction measurements. The influence of crosslinking units on phase behavior was discussed. The networks containing less than 8 mol% of crosslinking units showed elasticity, reversible phase transition and cholesteric grandjean texture. The glass transition temperatures increased and clearing temperatures decreased with concentration of crosslinking units.