Polymerizable monomeric reactants (PMR) type resins

A resin which comprises a mixture of:

• (a) nadic acid of Formula (Ia) or a derivative thereof ##STR13## (b) a diaminobisimide of Formula (Ib) ##STR14## (c) an aromatic tetracarboxylic acid of Formula (Ic) or a derivative thereof ##STR15## the components (a), (b) and (c) being present in the approximate molar proportions of 2:n:n-1;
• and
• wherein
• n is selected to provide a polyimide polymer of the desired size;
• Ar and Ar" may be the same or different and each represent an optionally substituted aryl, optionally substituted bridged or bonded di- or poly-aryl, or optionally substituted heteroaryl group;
• Ar' is an optionally substituted aryl or heteroaryl group which provides for good conjugation between the nitrogen containing groups;
• and
• X is an alkyl group or hydrogen.