Monomer composition comprising (i) acrylic monomers selected from the group consisting of (meth)acrylic acid and (meth)acrylic esters; (ii) orthoalkyl phenyl ketone- and/or orthoalkyl phenyl aldehyde-functionalized (meth)acrylate monomers; and (iii) optionally, further olefinically unsaturated monomers having functional groups; process for preparing a first polymer composition comprising the free-radical polymerization of the monomer composition, and polymer composition obtainable by this process; composition comprising the polymer composition and a dienophile which can react with hydroxy-ortho-quinodimethane functional groups in a Diels-Alder or hetero-Diels-Alder reaction and conversion of this composition to a crosslinked polymer composition.