Synthesis of hybrid polyimides from pyridine based monomers and investigation of their properties

The main scope of this thesis was to prepare and examine polyimide-organosilicate hybrid materials containing pyridine, bipyridine terpyridine and some pyridine derivatives. High temperature two-step solution polycondensation method has been successfully used to fabricate organosilicate hybrid materials. In addition, the effects of inorganic matrix on the thermal properties of polyimide hybrid materials were evaluated. The hybrid materials not only consisted of sol-gel derived organosilicate, organotitanate, but also phylosilicate domains covalently bonded to polyimide using partially hydrolyzed tetraethoxysilane (TEOS) or tetraethoxytitanate (TEOT). Thermally stable polyimide-clay nanocomposites were synthesized from reactive organophilic organoclay and poly(amic acid) by using N-methyl-2-pyrrolidone as a solvent. Montmorillonite clay mineral was used after being activated by means of sedimentation method. This clay consists of stacked silicate sheet therefore it is suitable for polyimide bonding. Thermal analysis showed that all types of polyimide nanocomposites have higher decomposition temperatures than classical polyimides. Polyimide-SiO2 hybrid materials were synthesized by sol-gel process with partially hydrolyzed tetraethoxysilane (TEOS) and a fully imidized polyimide functionalized with 3-aminopropyltriethoxysilane. PI-silica hybrid nanocomposites showed improved thermal stability and high mechanical properties. The glass transition temperatures of the hybrids increased with increasing content of silica or 3-aminopropyltriethoxysilane. Polyimide-TiO2 hybrid nanocomposites have also been successfully fabricated using tetraethoxyortotitanate and polyamic acid. All polyimides and hybrid as described above were structurally characterized by FTIR, X-ray spectroscopy and SEM. Other physical properties such as, density, viscosity, solubility and film forming properties were also determined. Physical properties revealed that the type of inorganic material incorporated into the hybrid would influence the viscosity, density, Tg, and thermal stability.