Synthesis And Characterization Of Fluorinated Liquid Crystalline Polymers And Elastomers

Due to the advantages of fluorinated liquid crystals, such as low viscosity, high resistivity, good stability, suitable dielectric constant, rapid response and so on, fluorinated liquid crystalline materials become very important in the display field.It is fluorine's small size, large electronegativety, and large fluorine-fluorine repulsion that lead to many excellent properties of fluorinated liquid crystals.Based on the different positions of fluorine atoms or fluorinated groups in molecules, fluorinated liquid crystals are classified in three species:liquid crystals bearing fluorine atoms or fluorinated groups as terminal groups, liquid crystals containing benzene ring with hydrogen atoms substituted by fluorine atoms, and liquid crystals with central bridge bond having hydrogen atoms substituted by fluorine atoms. According to the difference of liquid crystalline system in which they are, the changes of position and number in molecules, fluorine atoms make fluorinated liquid crystals possess diverse properties. At the same time, side-chain and terminal fluorinated compounds can raise the solubility of other liquid crystals in mix LCs due to fluorine's greasy solubility. For these reasons, fluorinated liquid crystals provide a wide choice for the deployment of various high-performance mixed-LCDs.In this dissertation, four liquid crystalline monomers were synthesized:two fluorinated monomers containing 4-Allyloxy-benzoic acid 4-[2-(3-trifluoromethy-phenoxy)-acetoxy]-biphenyl-4-yl ester and 4-allyloxy-benzoic acid 4-[2-(3-trifluoromethy-phenoxy)-acetoxy]-phenyl ester, two chiral monomers containing 3-(4-allylloxy-phenyl)-Acrylic acid cholesterol ester and 3-(4-Undecanoyloxy-phenyl)-acrylic acid cholesterol ester, they were referred to as M1, M2, M3 and M4. And then fluorinated monomers and chiral monomers were grafted to linear polymethylhydrogensiloxanes. So two series of fluorinated liquid crystalline polymers(LCPs) and one serie of fluorinated liquid crystalline elastomer(LCE) with different chemical structures and characters were synthesized. These three series were referred to as P1, P2 and P3. Furthermore, one main-chain liquid crystalline ionomers(LCI) were synthesized, and then the interaction between the sulfo inlaid in the mian chain and 4-fluoro-phenylamine generated a fluiorinated supreramolecular liquid crystals.The structures of the four obtained liquid crystalline monomers were analyzed and proved by FT-IR spectroscopy and 1H nuclear magnetic resonance (1H NMR). Results of specific rotation analysis(SRA) showed that chiral monomers M3 and M4 were all optical active. The phase transition temperature, enthalpy increment and mesogenic texture were studied with differential scanning calorimetry (DSC) and polarized optical microscopy (POM). Results of DSC and POM indicated that fluorinated monomer M1 was typical liquid nematic crystal; blue phase of wide temperature range appeared in fluorinated monomer M2 during the cooling process; chiral monomers M3 and M4 were all cholesteric liquid crystals, and had many advantages such as good thermal stability, wide mesomorphic temperature range and so on.The fluorinated superamolecule, fluorinated side-chain liquid crystalline polymers, and side-chain liquid crystalline elastomer were also investigated by IR, DSC, TG and POM. Results of analyses indicated that the polymers of P1 serie were all cholesteric liquid crystals; the polymers p2-1～P2-6 of P2 serie had excellent liquid crystalline properties; the polymers P3-1～P3-5 of P3 serie were also cholesteric liquid crystals. Polymers of these three series were all optical active, and had good thermal stability. The main-chain liquid crystalline ionomers(LCI) and the fluiorinated superamolecule were both liquid nematic crystals.