Aqueous solutions or aqueous emulsions of copolymers are obtainable by copolymerization of (a) from 20 to 95 mol % of at least one monoethylenically unsaturated C.sub.4 -C.sub.12 -dicarboxylic acid or the anhydride thereof with (b) from 5 to 80 mol % of at least one branched oligomer or polymer which has a vinyl, vinylidene or alkylvinylene terminal group and is of at least 9 carbon atoms and (c) from 0 to 50 mol % of at least one further monoethylenically unsaturated compound which is copolymerizable with the monomers (a) and (b) and contain from 0.5 to 70% by weight, based on the total amount of the solutions or emulsions, of these copolymers. These copolymer solutions or emulsions are suitable as leather assistants and as dispersants for pigments.

The specification discloses a method for making DCPD based resins that have relatively narrow molecular weight distributions. The method comprises thermally polymerizing dicyclopentadiene monomer in the presence of one or more strong acids, preferably with an olefinic modifier, to provide a dicyclopentadiene oligomer. Optionally, an organic sulfur species can also be used to further effect molecular weight control. For end-use performance in inks, adhesives, coatings and other related areas, the invention provides dicyclopentadiene oligomer resins having weight average molecular weights less than 1000 and relatively narrow molecular weight distributions, as measured by a polydispersity index, of less than about 2.3. Among the strong acids that are effective for controlling molecular weight, hypophosphorous acid is preferred because it gives light colored resins.