Chiral liquid-crystalline elastomers bearing side-chain fluorinated groups and chiral crosslinking units

摘要

Chiral fluorinated side-chain liquid-crystalline elastomers (LCEs) IP - IVP were graft copolymerized by hydrosilylation reaction. The chemical structure, liquid-crystalline behavior and polarization property were characterized by use of various experimental techniques. The effective crosslink density of the chiral LCEs was studied by swelling experiments. All the samples IP - IVP displayed chiral smectic C mesophase (S_C *) on heating and cooling cycles. With increasing chiral crosslinking units in the elastomer systems, the glass transition temperature and chiral smectic C mesophase-isotropic phase transition temperature of fluorinated elastomers increased slightly, indicating that the temperature range of S_C * mesophase became narrow with increase of chiral crosslinking agents for all the chiral fluorinated elastomers. All the samples IP - IVP showed 0.12-0.16 μC/cm~2 of spontaneous polarization.