Synthesis And Property Research On Siloxane-Containing Alicyclic Dianhydride And Polyimides With Good Solution And Low Water Adsorption

With the rapid development of electrical, electronic, aerospace, microelectronics industry, the needs of high temperature resistance polymer materials are becoming increasingly urgent.Traditional aromatic polyimide materials have excellect high and low temperature resistance properties, electrical properties, mechanical properties, radiation resistance and thermal stability. However, the electronic polarization and crystallinity of aromatic polyimide give rise to a strong intermolecular interaction and closed backbone molecular packing, so aromatic polymide materials are difficult to melt and solve, difficult to process. Moreover, the higher moisture resistance of PI was required in the microelectronics industry, and the microelectronics industry was limited due to the modest moisture resistance of traditional aromatic polyimide. Recently, the researches revealed that incorporation of siloxane and alicyclic segments proved effective to increase transparency, water ingression resistance, electrical property and solubility of PIs.According to above researches, the synthesis of a new siloxane-containing alicyclic dianhydride was reported in this paper. Meanwhile, a seies of siloxane-containing alicyclic polyimides were prepared by the new siloxane-containing alicyclic dianhydride and 4,4'-biphenyltetracarboxylic dianhydride (BPDA) togerher with 4,4'-oxydianiline (ODA), and the properties of PIs were researched.In the first step, 1,3-dimethyl-1,3-diphenyl disiloxane was synthesized by one-step, starting from 2,4,6,8-tetramethylcyclotetrasiloxane and phenyl Grignard reagent. Meanwhile, the bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid-2,3-dimethyl ester was synthesized by esterification of cis-5-norbornene-endo-2,3-dicarboxylic anhydride, methanol and 4-toluene sulfonic acid as the catalyst. Secondly, platinum complexes of methoxytriallylsilane as the catalyst of hydrosilylation was synthesized, starting from methoxytriallylsilane, chloroplatinic acid and sodium bicarbonate. Thirdly, a new siloxane-containing alicyclic dianhydride, 5,5'-exo-(1,3-dimethyl-1,3-diphenyl-disiloxane-1,5-diyl)bisbicyclo[2,2,1]heptene-2,3-endo-dicarboxylic anhydride was successfully synthesized by way of hydrosilylation, saponification, acidification and dehydration, starting from bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid-2,3-dimethyl ester, 1,3-dimethyl-1,3-diphenyldisiloxane and platinum complex catalyst. And the solubility of siloxane-containing alicyclic dianhydride was researched in this step. Meanwhile, research revealed that this synthetic route could, in a degree, increase the reactivity of hydrosilylation between reactants with high steric hindrance. Finally, a series of siloxane-containing alicyclic polyimides was prepared from dianhydride comonomers siloxane-containing alicyclic dianhydride and BPDA together with OD A in different molar ratio (0:1:1,0.25:0.75:1,0.33:0.66:1,0.5:0.5:1, 0.66:0.33:1,0.75:0.25:1,1:0:1) by a one-step high-temperature polycondensation method and the structures were characterized by IR. The effects of the main chain siloxane and alicyclic segments on the properties of PIs were evaluated by solubility, thermal stability and hygroscopicity.