The presently claimed invention is directed to a copolymer obtained by reacting at least one isocyanate (A) comprising at least one allophanate group and at least one active double bond with at least one isocyanate reactive component (B) to form an intermediate product (C); and reacting the intermediate product (C) with at least one active double bond reactive component (D) to obtain the copolymer which can be used as dispersant. The at least one isocyanate reactive component (B) is selected from the group consisting of monofunctional polyether amine (B1), monofunctional polyether alcohol (B2), C6-C30 monofunctional alcohol (B3) and monofunctional polyester alcohol (B4).