TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The cardo group comprises a bisphenyl fluorene group. The bismaleimide having a cardo group is (cc). The bismaleimide having a cardo group is present at 20 (preferably 0.1-10) wt% or less based on total weight of (I).    TECHNOLOGY FOCUS - POLYMERS - Preparation (Disclosed): Preparation of (I), comprises: reacting substituted amino-substituted bisphenyl fluorene compounds of formula (aa) with maleic anhydride in a solvent (e.g. tetrahydrofuran (THF)) at room temperature to give an amic acid intermediate compounds of formula (bb); converting (bb) in a solvent (e.g. THF) in the presence of a base (e.g. triethylamine) at an elevated temperature (preferably 40-80 degrees C (e.g. 60 degrees C)), to give the bismaleimide (BMI)-cardo compounds of formula (cc); and cross-linking (cc) in the presence of a thermoplastic polymer in the reaction medium (in a solvent (e.g. ethanol)) at room temperature to form (I).R1 = bond, residue of an ester or residue of an amide, preferably bond (preferred), -O-C(O)-R3 or -NH-C(O)-R3-;R2 = H or residue from an electrophilic aromatic substitution, preferably H (preferred), halo, -SO3H, -NO2, 1-10C alkyl or 1-10C acyl, where the alkyl or acyl groups are optionally substituted by -OH, -NH2, -NH(1-10C alkyl), -N-di(1-10C alkyl), -NH(6-14C aryl), =O, -O-(1-10C alkyl), -O-C(O)-1-10C alkyl, -NH-C(O)-1-10C alkyl or 6-14C aryl; andR3 = bond, 6-14C arylene (e.g. phenylene) or 1-10C alkylene (e.g. ethylene and propylene) (all optionally substituted by -OH, -NH2, -NH(1-6C alkyl), -N-di(1-6C alkyl), -NH(6-14C aryl), =O, -O-(1-6C alkyl), -O-C(O)-1-6C alkyl or -NH-C(O)-1-6C alkyl; andY1 = -OH or -NH2.Preferred Components: The thermoplastic polymer is a homopolymer or copolymer comprising a polyimide, polysulfone, polycarbonate, polyether oxide (all preferred), polyether sulfone, polyester, polyamide or polyketone. The thermoplastic polymer comprises polyetherimide (PEI) (preferred), Matrimid (RTM: Thermoplastic polyimide), 4,4'-hexafluoroisopropylidene bis(phthalic anhydride)/para-phenylenediamine, P-18 (RTM: Benzophenone 3,3',4,4'-tetracarboxylic acid dianhydride-toluene diisocyanate/4,4-Diphenylmethane diisocyanate copolyimide), Udel (RTM: Polysulfone), polyethersulfone, bisphenol A polycarbonate, polyphenylene oxide or polyethylene oxide containing polyimide. EXAMPLE - Polyetherimide (PEI) (24.75 g) was dissolved in anhydrous N-methyl-2-pyrrolidone (62.5 ml) by rolling the bottles at 60 degrees C. To the completely dissolved PEI solution, anhydrous ethanol (12.5 ml) was added and mixed again until a homogeneous solution was obtained. 9,9-Bis(4-maleimidophenyl)fluorene (0.25 g) was added to this and the solution was rolled at 60 degrees C to obtain semi-interpenetrating polymer network.