Synthesis And Characterization Of Side-chain Liquid Crystalline Polysiloxane

Side-chain liquid crystal polysiloxane is a kind of liquid crystal polymers which main chain is composited by -Si-O- bond, and the mesogenic groups are connected by flexible spacer groups in the polymer main chain. A series of liquid crystal polymers that the liquid crystal phase transition temperature from low to high , the LCD temperature range from narrow to wide, the liquid crystal phase from smectic to columnar phase. It is given by the diversity of the properties of side chain liquid crystal polysiloxane such as thermotropic liquid crystal, the better threshold characteristics and response characteristics; and its orientation state can stable in the absence of electric for a long time. Base on these characteristics of side chain liquid crystal polysiloxane, it is studied depth in recent years, and the research has been made great progress.In this dissertation, seven monomers were synthesized. Different kinds of mesogenic monomers (including blue phase monomers, smectic monomers and nematic monomers) were grafted to linear polymethylhydrogensiloxanes. So nine kinds of SCLCPs with different chemical structures and characters were synthesized.The structures and properties of the obtained liquid crystalline monomers and polymers were investigated by FT-IR spectroscopy, 1H-NMR spectroscopy, differential scanning calorimetry (DSC), polarizing optical microscopy (POM), X-ray diffraction (XRD) and thermo gravimetric analyses (TGA).Monomers 3HHV, 4HHV and 5HHV use double-cyclohexane as mesogenic; they present multi-color small plate blue phase, nematic phase and smectic phase. Monomers M1, M2, M3 and M4 use cyclobenzene as mesogenic; they present nematic phase and smectic phase. The ranges of temperature of liquid crystalline phase of monomers are wide. The monomers have excellent liquid crystalline properties and good thermal stability. In the series of polymer P₁, P_1-1 is cholesteric liquid crystal polymer, P_1-2 is both blue phase and nematic liquid crystal polymer, P_1-3 is blue phase liquid crystal polymer. In the series of polymer P₂, P_2-1 is blue phase liquid crystal polymer, P_2-2 is both blue phase and smectic liquid crystal polymer, P_2-3 is blue phase liquid crystal polymer. Polymer P₁ and P₃ are smectic liquid crystal polymers, polymer P₂ and P₄ are nematic liquid crystal polymers. The ranges of temperature of liquid crystalline phase of polymers are wide. The polymers have excellent liquid crystalline properties and good thermal stability.