Study of polyimides containing flexible groups

A series of flexible polyimides has been investigated with regard to the physical properties before and after swelling with supercritical carbon dioxide. Also it was determined the thermal stability and dynamo-mechanical properties of the polymers. The study of the dependence of glass transition temperature and free volume of polymers on their conformational rigidity showed that the process of swelling in supercritical carbon dioxide is influenced by the voluminous side groups and by the high boiling solvent N-methylpyrrolidinone used for the preparation of the polymers, which facilitates the formation of crosslinks or complexes with the macromolecular chains. All the polymers showed high thermal stability, with decomposition temperature above 400degC and glass transition above 200degC. They exhibited a reasonable interval between glass transition and decomposition, which can be advantageous for their processing.