Study On Colloidal Liquid Crystal Of Hydroxyapatite And Its PVA Composite

The hierarchical structure formed by nano-hydroxyapatite and bone collagen fibers in bones is very similar to the ordered structure of anisotropic nano-units in inorganic liquid crystals.Inspired by its similarities,the thesis explores the behavior of hydroxyapatite liquid crystals.In this thesis,the liquid-solid-solution(LSS)synthesis strategy is adopted,and the one-dimensional hydroxyapatite nanoparticles with uniform morphology and good dispersion effect are successfully prepared by hydrothermal method assisted by oleic acid or sodium citrate Particles,and studied the liquid crystal phase transition and the properties of composite materials.In the thesis,the effect of the molar ratio of oleic acid to ethylenediamine and oleic acid to calcium salt,hydrothermal time and hydrothermal method on the product morphology was first studied,and the experimental conditions for preparing nano-hydroxyapatite particles were preliminarily explored.Subsequently,the experimental scheme was optimized.The effect of hydrothermal mode on the synthesized particles was systematically studied.The oil-soluble hydroxyapatite nanoparticles prepared under the optimal experimental conditions were selected to investigate the liquid crystal behavior.The research results show that the particles prepared in the three-necked flask under low temperature and normal pressure hydrothermal treatment are in the form of thin wires,the length is 228.23±99.22 nm,and the dispersion has no obvious precipitation when the concentration in cyclohexane is 1wt%;The particles prepared after hydrothermal treatment in the vinyl fluoride reactor were in the form of regular short rods with a length of 51.46±31.37 nm,and their 1wt% dispersion had significant sedimentation.When the mass concentration of the dispersion is increased,the particles after three-necked flask low-temperature and normal-pressure hydrothermal treatment can undergo an isotropic phase to liquid crystal phase transition,with a critical concentration of 15.2wt%.However,the particle dispersion after the high-temperature and high-pressure hydrothermal treatment of polytetrafluoroethylene cannot exhibit liquid crystal phase transition,which is preliminarily believed to be the result of the relatively low long diameter of the prepared particles.In addition,the particles synthesized in the three-necked flask can also exhibit similar liquid crystal behavior transitions in other non-polar solvents.Finally,the thesis used the prepared water-soluble hydroxyapatite to explore the properties of the composite material with polyvinyl alcohol(PVA).The experimental results show that the content of HA in the prepared HA-PVA composite membrane material has certain mechanical properties Degree of influence.However,the prepared HA-PVA bulk material can control the thickness of the material after hot pressing,and exhibits a very strong liquid crystal texture under polarized light.These results indicate that this composite material has important application prospects in the fields of medicine and biology.