Abstract: Oligomers of the formula ##STR1## wherein: (1) at least one A=--CH.sub.2 CHR.sup.1 COODOH (a) (R.sup.1 =H, CH.sub.3 and D=C.sub.1 -C.sub.4 alkylene), the other A's=H or C.sub.1 -C.sub.4 alkyl, it being possible for at least a part of the residues (a) to be converted into A.sup.1 =--CH.sub.2 CHR.sup.1 COODOCONHD.sup.1 NCO (D.sup.1 =divalent organic residue), it being possible for at least a part of the residues A.sup.1 to be converted into A.sup.2 =--CH.sub.2 CHR.sup.1 COODOCONHD.sup.1 NHCOOR.sup.2 (R.sup.2 =monovalent radical obtained by removal of OH from a monoalcohol containing a vinylidene group);(2) at least one A=D.sup.2 OCONHD'.sup.1 NHCOOR'.sup.2 (b) where D.sup.2 =C.sub.1 -C.sub.4 alkylene or --D.sup.3 --(--O--D.sup.3 --).sub.n --, with D.sup.3 =C.sub.1 -C.sub.4 alkylene and n=1-12; D'.sup.1 analogous to D.sup.1 ; R'.sup.2 analogous to R.sup.2 ; the other residue(s) A denoting --D.sup.2 OCONHD'.sup.1 NCO.