Synthesis And Mesogenic Properties Of Side-chain Liquid Crystalline Polymers Containing Nitrogen And Sulfur Atoms

The side-chain liquid crystalline polymers (SLCPs) containing nitrogen and sulfur atoms continue to be the subject of research. The liquid-crystalline compounds containing sulfur atom can be adsorbed spontaneously by chemisorption on the metallic surface such as Au, Pt, Ag etc. to form monolayer-modified surface which give better understanding of the self-assembly in molecular systems.In addition, due to the chelating properties of sulfur atoms, they have the ability in adsorbing some weight and noble metal ions such as Au³⁺, Ag⁺, Cu²⁺etc, especially, the selective adsorption towards a certain mental ions after quenching.Thioether structure can contribute to the formation of thermotropic liquid crystalline phase and increase the stability. When inserted in the carbon-based main chain or spacer, the thioether unit can enhance the flexibility of the backbone or spacer and remove the crystallization phenomenon of copolymers owing to the C-S bond with longer length and weaker bond strength, therefore, resulting in broader mesophase rangesThis paper sumarrizes the developed history for liquid crystalline compound, the structure typise and corresponding models, application fields and developing trend about liquid crystalline polymers. Three series of monomers containing two kinds of mesogenic groups have been synthesized, which reacted with three series of main chain backbones to give four series of side chain liquid crystalline copolymers. The structures of the synthesized monomers and polymers were confirmed by elemental analysis, IR and ¹H NMR spectroscopy. The thermal properties of these polymers have been investigated using differential scanning calorimetry (DSC), polarizing optical macroscopic (POM), X-ray diffraction and thermogravimetric analysis (TGA). The main context are as follows:The monomers, 1-Bromo-co-(4-methoxyazobenzene-4'-oxy)alkanes, have been synthesized in which the number of methylene unit varies from 2 to 6. The structures of the synthesized monomers were confirmed by IR and ¹H NMR spectroscopy. The thermal properties of these polymers have been investigated using differential scanning calorimetry (DSC), polarizing optical macroscopic (POM), the effect of he number of methylene unit on the thermal properties has been studed. The thermal stability increased with the increase of methylene number.The novel polymers, Poly [N-(4-methoxyazobenzene-4'-oxyalkyl)ethyleneimi-ne] (PEnZO), has been synthesized by the reaction of synthesized monomers with poly ethyleneimine in which the number of methylene unit in spacer varies from 2 to 6. The structures of the synthesized monomers and polymers were confirmed by IR and ¹H NMR spectroscopy. The thermal properties of these polymers have been investigated using differential scanning calorimetry (DSC), polarizing optical macroscopic (POM), X-ray diffraction and thermogravimetric analysis (TGA). Especially, the effect of solution on the substitution degree was investigated.The test results indicated that the obtained polymers exhibited thermotropic liquid crystalline mesomophism of nematic type with schlieren textures. A more pronounced odd-even effect in the melting points and their enthalpy changes was observed on increasing the spacer length in which the odd members displayed lower values, which were also slightly dependent on the substitution degree of polymers.(4-Methoxyazobenzene-4'-oxy)alkylthiol have been propertied by the reaction of thiourea with the obtained monomers. Their structure were confirmed byelemental analysis and ¹H NMR spectroscopy. The thermal properties of these polymers have been investigated using differential scanning calorimetry (DSC), polarizing optical macroscopic (POM). The test results indicated that the obtained polymers exhibited thermotropic liquid crystalline mesomophism of nematic type with schlieren textures.The reaction of obtained thiols with polyepichlorohydrin yields [1-({(4-methoxyazobenzene-4'-oxy) alkyl} thio)-2.3-epoxypropane]s, in which the number of methylene unit in alkyl group of side-chain varies from 3 to 6. The structures of compounds obtained were characterized by ¹H NMR. The thermal properties were investigated using polarized optical microscopy, differential scanning calorimetry and X-ray diffraction analysis. The copolymers exhibited thermotropic liquid crystalline behaviour and presented nematic phases with Schlieren textures.Owing to the unusual structural rearrangement of polychloromethylthiirane (PCMT) at room temperature, it has not been found to be used as the main-chain backbone of side-chain liquid crystalline polymers (SLCPs). However, it was observed that PCMT has a relatively stable and clear structure under special conditions. New polymers, poly [1-({(4-methoxyazobenzene-4'-oxy)alkyl}thio)-2,3-epithiopropane] (PSSnZO), in which the number of methylene units in the alkyl group is 4,5 and 6, respectively, have been prepared by means of reactions of obtained thiols with PCMT. The structures of these compounds were confirmed by elemental analysis and ¹H NMR spectroscopy. DSC measurement and POM observation showed that the resulting copolymers exhibited thermotropic liquid crystalline mesomophism with nematic phase.A novel series of copolymers, Poly[1-(4-(Benzothiazole-2-thio-alkyloxy)-biphenyl-4'-oxy)2.3-epoxypropane]s, have been synthesized by the reaction of polyepichlorohydrin with 4-(Benzothiazole-2-thio-alkyloxy)biphenyl-4'-ol, in which the number of methylene unit in substitution group of biphenyl group varies from 2 to 6. The structures of compounds obtained were confirmed by elemental analysis and ¹H NMR. Differential scanning calorimetry (DSC) measurement and polarized optical microscopy (POM) observation showed that the resulting copolymers didn't exhibite thermotropic liquid crystalline mesomophism.