Studies On The Synthesis And Properties Of Organosilicone Functionalized Monomer And Polyimide Materials Prepared Via Hydrosilylation Reaction

Polyimides(PIs),a well-known class of high performance polymers,have found various applications in many high-tech fields owing to their excellent combined physical and thermal properties.However,their application is some what limited due to difficulties such as insolubility in conventional solvents and extremely high glass transition temperature or high melting temperature.Therefore,significant efforts in the area of structure modification have been made to minimize the disadvantages and improve application performance.In general,silicone-containing polyimides possess high thermal,and oxidative stability and exhibit good adhesive and electrical properties for various applications.For one thing,the solubility of PIs can be increased by the introduction of flexible linkages,large pendent groups or non-polar substituents into the polymer.Among the substituents,siloxane has been widely utilized to develop polymers with good solubility.For another,polysiloxane materials render a number of useful properties such as low temperature flexibility,high thermal stability,hydrophobicity,oxidative resistance,biocompatibility,high adhesiveness,low dielectric constants and significant gas permeability.Thus the incorporation of siloxane groups into the aromatic polymer chains yielded soluble products having remarkable thermal stability and good film-forming ability.In this paper,we prepared new polyimides in structure modification containing main chain siloxane groups to investigate the properties of materials.Silicone-containing polyimides are usually synthesised via a condensation of silicon containing monomers,i.e.diamines or dianhydrides.In this thesis,we suggest another possibility,typical for silicon containing polymers,the polyhydrosilylation reaction of an imide with two terminal alkene groups.The hydrosilylation reaction is an important reaction in organosilicon chemistry.It may proceed thermally or in the presence of variety of catalysts e.g.hexachloroplatinic acid.Firstly,in the present study we synthesised two kinds of copolyimides of general formula given below carrying imide moieties and 1,1,3,3-tetramethyldisiloxane unit.The introduction of siloxane segment to polyimide backbone was found to improve the solubility and melt processability of polyimide.The products were structurally characterized by FT-IR and 1H-NMR techniques.The thermal properties and molecular weight of targe siloxane-containing polyimide were studied by Thermogravimetric analysis(TGA),differential scanning calorimetry(DSC)and size exclusion chromatography(SEC).Secondly,we developed a novel and convenient synthetic method to prepared the diamine of 1,3-bis(3'-aminopropyl)-1,1,3,3-tetramethyldisiloxane(PTDS).It was synthesized via a three-step method.In the second step,imide ring were introduced to the siloxane backbone via hydrosilylation.In the third step,Gabriel reaction was used for ring-opening then give the desired primary amine and the side product phthalyl hydrazide.PTDS modified Polyimides were synthesized via copolymerization with PTDS and ODA reacted with ODPA.And the Polyimides were studied for thermal properties,dynamic mechanical properties,solubility and optical properties.Its organic solvents solubility and transparency of PTDS modified Polyimide were significantly improved with the addition of siloxane PTDS increased.Thermal stability of PTDS modified Polyimide was a little depressed with the addition of PTDS siloxane.But the 5%decompound temperature of PTDS modified Polyimides were all above 450?,show excellent thermal stability.With the content of PTDS siloxane increasing,the PIs revealed higher optical transparency and lighter colour.