Preparation,Structure And Properties Of Organic-inorganic Nanocomposites Containing Oligomer Silsesquioxane

Organic-inorganic hybrids have been rapidly developed due to their comprehensive characteristics through the synergism of organic and inorganic materials.Polyhedral oligomeric silsesquioxane(POSS)is a class of interesting nanobuilding blocks,which possess a cage or ring-like structure inorganic Si-O frameworks and covalently bonded organic ligands to each Si atom.In addition,it can be easily functionalized according to the different requirments,which makes it feasible to prepare organic-inorganic hybrid materials.Organic-inorganic hybrid materials can be prepared via two methods: chemical method and physical blending method.It is noted that due to the difference of compatibility between organic and inorganic materials,physical blending method may lead to macrophase separation of materials.In comparision,chemical method is an effective to afford organic-inorganic nanocomposites.In this method,oligomer silsesquioxane can be functionalized to bear the reactive groups,which can significantly improve the compatibility between the inorganic units and the organic matrix.Double decker silsesquioxane(DDSQ)is a class of POSS molecules.In this thesis,we attempted to synthesize four functional oligomer silsesquioxane(denoted DDSQ)via a series of chemical reactions,such as silylation,hydrosilylation and Heck reaction.The obtained DDSQ was introduced to different materials to prepare organic-inorganic hybrid composites.The main research works are as follows:1.Synthesis,structure and properties of DDSQ-contaning polyimide nanocomposites.5,11,14,17-tetraanilino DDSQ was synthesized via a Heck reaction between 5,11,14,17-tetravinyl DDSQ and 4-bromoaniline.Subsequently,this kind of DDSQ was introduced into polyimide to prepare organic-inorganic hybrid polyimides.The organic-inorganic hybrid polyimides displayed microphase separated structure,in which DDSQ was dispersed in the polyimide matrix as a form of nanodomains.The effects of DDSQ on thermal and hydrophobic properties of polyimide materials were investigated by thermogravimetry(TGA)and contact angle test.The incorporation of DDSQ improved the thermal stability and the surface hydrophobicity of the materials.Furthermore,the dielectric properties of materials were investigated by dielectric impedance.It was displayed that the incorporation of DDSQ significantly decreased the dielectric constants of the materials.2.Preparation,structure and properties of DDSQ-containing epoxy thermosets and polybenzoxazines.1)DDSQ-containing epoxy thermosets were prepared by using 5,11,14,17-tetraanilino DDSQ as curing agent.Transmission electron microscopy(TEM)results indicated that DDSQ was dispersed in the epoxy matrix as a form of nanodomains.The incorporation of DDSQ affected the properties of the materials,which was reflected by the improved thermal stability and reduced dielectric constants.2)DDSQ-containing polybenzoxazines were prepared by a reaction of 5,11,14,17-tetraanilino DDSQ,phenol and paraformaldehyde.The microphase separation structure,thermal properties and dielectric properties of the composites were also investigated by TEM,dynamic mechanicl thermal analysis(DMTA),TGA and dielectric impedance in detail.3.Synthesis,structure and properties of DDSQ-containing polyhydroxyurethane.First,DDSQ-containing cyclic carbonate was prepared via a hydrosilylation of 5,11,14,17-tetrahydrogen DDSQ and allyl cyclic carbonate.Thereafter,DDSQ-containing cyclic carbonate was reacted with polyetheramine(T403)to obtain DDSQ-containing polyhydroxyurethane.The morphological structures of the material were investigated by scanning electron microscope(SEM).DDSQ formed nanodomains of 0.5 ?m in the polyhydroxyurethane matrix.The incorporation of DDSQ significantly improved the thermal properties of the materials,which were evidenced by TGA and DMTA.Furthermore,the results of contact angle test displayed that the existence of DDSQ improved the surface hydrophobicity of the materials.