Process for preparing polyurea oligomers

A process for preparing a polyurea oligomer of Formula I ##STR35## wherein:

• R represents a hydrogen atom, a C.sub.1 -C.sub.4 alkyl group, a phenyl group, or a phenyl group substituted with from 1 to 1 R.sup.1 moieties and up to 3 substituents independently selected from a chloro or bromo atom or C.sub.1 -C.sub.4 alkyl group;
• R.sup.1 represents a --SO.sub.3 R.sup.2, --CO.sub.2 R.sup.2, --PO.sub.3 (R.sup.2).sub.2, or --OPO.sub.3 R.sup.2 ;
• R.sup.2 represents a hydrogen atom or a pharmaceutically-acceptable cation;
• m is an integer 0 or 1, with the proviso that when m is 0, R is a hydrogen atom;
• X represents ##STR36## Y represents --CO.sub.2 --, --C.tbd.C--, --N.dbd.N--, ##STR37## n is an integer from 3 to 50;
• and R.sup.3 represents --R or --X--NH.sub.2, where R and X are defined as before;
• which comprises reacting an aromatic diamine with a difunctional electrophile, in the presence of an acid acceptor, in water as the solvent or water with up to about 1 mole of water immiscible cosolvent, at a temperature of from about 0.degree. to about 100.degree. C. and at a pH between about 7 to about 9;
• and
• wherein by careful adjustment of the stoichiometry of the reactants or using a monofunctional end capping agent the polyurea oligomer prepared has a number average molecular weight of less than 10,000 and is water-soluble.