The Research On Functionalization And Liquid Crystals Composite Of Multi-walled Carbon Nanotubes

Caron nanotubes (CNTs) have attracted enormous attention due to their excellent mechanical properties, unique microstructure, high specific surface area and aspect ratio. The properties of composites can be effectively improved by the addition of only a few CNTs. The introduction of CNTs into the liquid crystal matrix has been a topic of intensive studies in recent years. Though some progresses on fabricating CNTs/liquid crystals composite have been achieved during the past few years, several principle problems have not been got over by now. CNTs cannot be dispersed uniformly in matrix and a firm interfacial adhesion between CNTs and liquid crystals cannot be formed due to their poor compatibility. Thus, in order to take full advantage of CNTs in modified composites, CNTs should be availably funcionalized. For this purpose, this paper conducted studies as follows.(1) The aromatic amide liquid crystals (LC-A) molecules were prepared in good yields by a special solution condensation of p-methoxybenzoic acid and diamine in a mixture of triphenylphosphine, pyridine and hexachloroethane, and then LC-A was modified with NBS to yield bromic liquid crystal molecule (LC-B). The molecular structure of LC-A and LC-B was confirmed by FT-IR and 1HNMR spectroscopy. DSC and POM indicated that LC-A and LC-B are thermotropic liquid crystalline with typical smectic mesophase.(2) A novel na nocomposite of the liquid crystal molecules'waist positions anchored on the surface of multiwall carbon nanotubes (MWNTs) was prepared by using a dissolving metal reduction method. The formation of the LC-MWNTs composite was confirmed by both Raman and FT-IR spectroscopy. HRTEM demonstrates that the liquid crystals molecules are anchored on the surface of MWNTs via covalent linkage, with a wrapped thickness approximately 3-5 nm. The loss-weight fraction of the LC layers for the LC-MWNTs can be roughly estimated as 23% by TGA. The experiments of solubility exhibit that the LC-MWNTs forms a stable suspension solution in polar solvents such as dimethylformamide.(3) MWNTs/LC-A and LC-MWNTs/LC-A nanocomposites were prepared via solution blend. SEM shows that LC-MWNTs disperse well and the agglomeration of MWNTs is appeared in LC-A matrix, which demonstrates LC-MWNTs have better compatibility with LC-A than that of MWNTs with LC-A.(4) TGA presents the thermal stability is LC-MWNTs/LC-A composites, MWNTs/LC-A composites, LC-A in sequence. DSC shows with the increase of the content of LC-MWNTs, the melt point (Tm) of composites has a tendency of decrease at first and then increase, and when the content of LC-MWNTs is 0.5wt%, the Tm of composites decreases by 18℃. POM results indicated LC-MWNTs/LC-A composites have more smectic mesophase LC texture than LC-A, and the selforganizing property of LC-A induces the alignment of dispersed LC-MWNTs.