NOVELTY - Preparing low-melt viscosity imide oligomers derived from solvent-free reaction of stoichiometric effective amounts of at least one asymmetric dianhydride (I) and at least one aromatic diamine (II) and endcap comprising 4-phenylethynylphthalic anhydride or cis-5-norbornene-endo-2,3-dicarboxylic anhydride, comprises:(a) introducing the dianhydride, the diamine, and endcap into extruder at its throat; (b) melt mixing them in at least one mixing zone having at least one temperature to thoroughly blend them together and to permit concurrent reaction; and (c) extruding.    USE - The process is useful for preparing low-melt viscosity imide oligomers which are useful for forming composite, where the composite is in the form of an article comprising airframe component, engine component, aircraft, missile, radome, rocket, high temperature laminate, electrical transformer, engine bushing, engine bearing, oil drilling equipment, oil drilling risers, automotive chassis bearings, and films for use in electronics, fuel cells and batteries (all claimed).    ADVANTAGE - The process provides low-melt viscosity imide oligomers (in the form of dry powders, pellets, filaments, films) from dianhydrides and diamines via concurrent reactive extrusion. The diamine is subjected to end-capping to minimize over-reaction of the dianhydride with the diamine.    DETAILED DESCRIPTION - Preparing low-melt viscosity imide oligomers derived from a solvent-free reaction of stoichiometric effective amounts of at least one asymmetric dianhydride of formula (I) and at least one aromatic diamine (II) of formula (IIa) or (IIb) and endcap comprising 4-phenylethynylphthalic anhydride or cis-5-norbornene-endo-2,3-dicarboxylic anhydride, comprises:(a) introducing the asymmetric dianhydride, the aromatic diamine, and the endcap into an extruder at its throat; (b) melt mixing the asymmetric dianhydride, the aromatic diamine, and the endcap for period of time in at least one mixing zone having at least one temperature to thoroughly blend them together and to permit concurrent reaction of both the asymmetric dianhydride and the endcap with the diamine to form the imide oligomer; and (c) extruding the imide oligomer from the extruder.    X = absent, C=O, -CH2 or O; and    Y1 = absent, CH2, C2H4, C=O, or O.    An INDEPENDENT CLAIM is also included for a composite formed from the imide oligomer made by the process.