The present invention relates to a monolithic organic copolymer prepared by copolymerization of at least one monomer of the group consisting of styrene, (C1-C3)alkylstyrene, (meth)acrylic acid and esters thereof with a crosslinker in the presence of a macroporogen and a microporogen, wherein a) the sum of said at least one monomer of the group and the crosslinker is 10-20%, preferably 10-15%, by volume of the reaction mixture, with the rest being essentially macroporogen and microporogen, and the degree of said copolymerization is at least 70%, preferably at least 90%, more preferably at least 99%, or b) the sum of said at least one monomer of the group and the crosslinker is 30-50%, preferably 35-45%, by volume of the reaction mixture, with the rest being essentially macroporogen and microporogen, and the degree of said copolymerization is in the range of 25-60%, preferably 35-50%. These copolymers can be used in high-performance liquid chromatography for the separation of biopolymers as well as small molecules.