Synthesis of a new siloxane‐containing alicyclic dianhydride and the derived polyimides with improved solubility and hydrophobicity

The structural transformation strategy of cis‐5‐norbornene‐endo‐2,3‐dicarboxylic anhydride (NA) was performed by esterification. The double bond on the diester of NA showed adequate hydrosilylation reactivity with Si? H bonds of phenyl‐containing disiloxane. Thereby, a new siloxane‐containing alicyclic dianhydride, 5,5′‐exo‐(1,3‐dimethyl‐1,3‐diphenyl‐disiloxane‐1,5‐diyl)bisbicyclo2,2,1]heptane‐2,3‐endo‐dicarboxylic anhydride 6 was successfully synthesized starting from NA, 1,3‐dimethyl‐1,3‐diphenyldisiloxane and platinum complex catalyst. The whole synthetic route of dianhydride 6 consisted of esterification, hydrosilylation, saponification, acidification, and dehydration. A series of polyimides (PIs) were prepared from dianhydride comonomers of 6 and 4,4′‐biphenyltetracarboxylic dianhydride (BPDA) in different molar ratio together with the diamine 4,4′‐oxydianiline (ODA). The thermal and mechanical properties of PIs showed somewhat decrease with increasing content of dianhydride 6. The solubility of PIs increased with the increasing content of dianhydride 6, and further calculation from Bragg's equation indicated that average interchain distance (d‐spacing value) increased with increasing content of siloxane and alicyclic segments in the backbone of PIs. It was revealed that the hydrophobicity of PIs increased with the increasing content of dianhydride 6 . Polyimide 7g , which was prepared from 100% 6 and ODA, showed water adsorption of less than 0.7% and contact angle against water of 101.1°. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci., 2013