Studies on the preparation characterization and properties of polyimides containing thiophene dithiane pyrimidine

Abstract

The present research proposal is focused on the synthesis and characterization of soluble and thermally stable polyimides, bismaleimides, and polyaspartimides having bulky pendant groups and flexible linkages on the polymer chain. Seven different diamines containing thiophene, dithiane, pyrimidine, pyridine and naphthalene units were prepared. The diamine monomer containing thiophene as pendant group was prepared by three steps. Seven different bismaleimides were synthesized from the prepared diamines with maleic anhydride (in the presence of sodium acetate as catalyst and acetic anhydride as dehydrating agent). Polyimides were synthesized by one step method and two step method (both thermal and chemical imidization) by solution polycondensation technique using the synthesized diamine with different dianhydrides such as PMDA and BTDA. The number average molecular weight, weight average molecular weight and polydispersity index of the polyimides and polyaspartimides were determined in THF using Gel permeation chromatography. The results reveal that these polymers are of good molecular weight to fabricate polymer films. The order of moisture absorption was found to be BTDA-PIgtPMDA-PI.The thermal stability of the polyimides, polyaspartimides and cured bismaleimide resins were ascertained by thermo gravimetric analysis. The thermal stability of these resins was compared by the temperature of 10% decomposition (T10%) and percentage char yield at 800oC. Thermal transitions of BMIs viz the melting points, the polymerization temperatures (the thermally induced polymerization of the obtained BMI compounds could be observed from the exothermic peaks) and the processing windows of the obtained compounds were measured by DSC. The glass transition temperature of the polyimides and polyaspartimides depends upon the segmental rigidity of the polymer backbone, as evident from the results. All these properties, associated with an easy processability make the present polymers potential candidates for high performance applications.