ABSTRACT
The solid-state synthesis of polyimides from 'nylon-salt' (carboxylic acid-amine salt) type monomers (Scheme 1) is a well-established technology [1, 2] that has recently been reactivated by Irnai and co-workers [3] using high-pressure polycondensation methods. Currently, the most popular method of polyimide synthesis employs high boiling dipolar aprotic solvents such as dimethylformamide (DMF), dimethylacetamide (DMAc) and N-methylpyrrolidone (NMP) at low temperature for the poly(amic acid) formation step and then cyclodehydration of the poly(amic acid) to the polyimide at elevated temperature. The use of water as solvent for polymerisation has been previously discounted by the perception that polyimides were somewhat susceptible to hydrolysis. This is despite considerable evidence to the contrary from the severe conditions required for the hydrolysis step in the Gabriel synthesis [4] and recent composite degradation studies [5]. The other perceived problem in using water as solvent for polyimide synthesis is the
poorsolubilityofmostpolyimidesinwaterunderambientconditions.Hence,the conceptofutilisingwaterassolventforpolyimidesynthesisisusuallydismissed withacertainlevelofincredulity.
