Effect of Palladium Coordination on Liquid Crystallinity of Imine Side Chain Polysiloxane

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Abstract
A new type of Pd-coordinating imine side chain liquid crystalline polysiloxane (Pd-ImLCP) has been synthesized by hydrolyzation reaction of N-(4-n-undecylenoxy-benzylidene)-4-dodecyloxyaniline with polymethylhydrogensiloxane (PMHS), then by ortho-palladation reaction of the obtained polymer ligand, imine side chain liquid crystalline polysiloxane (ImLCP), with various amounts of palladium acetate. The corresponding low molar mass Pd-coordinating imine complex (Pd-Im) has been also prepared for comparison. Their mesomorphic properties have been studied by polarizing microscopy, DSC and X-ray diffraction methods. The incorporation of Pd ions into the macromolecules ImLCP can affect the mesophase transitions in different ways. By increasing the molar percentage of Pd in the polymer, the textures turn from smectic to nematic phases and the transition temperatures almost stay constant up to 27 mole% and then decrease to 80 mole% at which crosslinking occurs. The clearing temperatures Tcl and enthalpy changes ΔHi are lowered with rising molar percentage of Pd in the polymer. These results show a negative effect of coordinated Pd ions on the liquid crystallinity of the polymer ligand.