Cage Silsesquioxane Synthesis And Hybrid Materials Research

Nowadays, preparation of hybrid materials from polyhedral oligomeric silsesquioxane (POSS) derivates attracts much attention, owing to their excellent optical properties, thermal resistance, flame retardance, high hardness, and abrasion resistance. POSS is a category of organosilicon compounds with peculiar molecular structure. It has a well-defined cage-like molecule having an inorganic silica-like core, which is surrounded by seven or eight organic hydrocarbon groups. The inorganic core provides it with high thermal stability, while the organic groups endow it with good compatibility with the organic matrix. Organic inorganic hybrid materials of molecular level with a inorganic silica-like core can be obtained using POSS as the precursor. Besides, POSS compounds show great potentials in many areas such as light cured resins, catalyst carrier, flame-retardants, plastics fillers and so on. However, the synthetic technology has been still not mature, which greatly precludes the further study, development and application of this nanomaterial. So, it is very necessary to study the synthetic conditions and influencing factors for the synthesis of POSS, especially for functional POSS. On consideration of this situation, three sections of work have been done in this dissertation.Firstly, cage-like octa(aminosilsesquioxane) was synthesized by the hydrolic condensation of aminopropyltrioxyethylsilane. Optimum synthetic conditions were determined after perpendicular experiment and single factor analysis used to evaluate the effects of experimental parameters on the synthesis. The resultant product was purified in the light of solubility difference and was characterized by FTIR, NMR, XRD and element analysis. And the molecular structure of octa(aminosilsesquioxane) was calculated and optimized using Gaussian 2003 software.Secondly, functional octa(aminosilsesquioxane) reacted with thermosetting epoxy resin to synthesize uniform hybrid resin, which was cured afterward to obtain organic inorganic polymeric hybrid materials, in which inorganic components bonded covalently with organic matrix and dispersed uniformly. Its structure, curing behavior and the effect of POSS-NH₂ on the reactivity of the hybrid resin were studied. The curing kinetics of hybrid resin was studied in detail by means of dynamic DSC.Finally, the as obtained hybrid material containing POSS-NH₂ was studied in respect to mechanical properties, thermal stability, hot-oxygen resistance, density and dimension stability. The effect of POSS-NH₂ on the properties of materials wasdiscussed. It was found that certain content of POSS-NH2 could increase the impact and flexural strength at the same time. And POSS-NH2 could improve the thermal stability, reduce the density and enhance the dimension stability of hybrid materials. In addition, SEM was used to explore the strengthening and toughening mechanism of POSS-NH2 as well its ability to enhance hot-oxygen resistance of hybrid materials. At last, the thermadegradation kinetics of hybrid materials was studied in detail.