Copolymers of olefinically unsaturated monomers, their preparation and use

Disclosed herein is a copolymer (A) of olefinically unsaturated monomers (a), prepared by single-stage or multistage controlled free-radical copolymerization in an aqueous medium of monomers comprising: (a1) an olefinically unsaturated monomer comprising a chelate-forming group; and (a2) an olefinically unsaturated monomer different from the olefinically unsaturated monomer (a1), and selected from the group consisting of: (a21) monomers of the general formula I: R1R2C-CR3R4 (I), wherein R1, R2, R3, and R4 are independently hydrogen atoms or substituted or unsubstituted alkyl, cycloalkyl, alkylcycloalkyl, cycloalkylalkyl, aryl, alkylaryl, cycloalkylaryl, arylalkyl or arylcycloalkyl radicals, with the proviso that at least two of R1, R2, R3, and R4 are substituted or unsubstituted aryl, arylalkyl or arylcycloalkyl radicals; (a22) an olefinically unsaturated terpene hydrocarbon; and (a23) a dimeric alpha-alkylvinylaromatic. Also disclosed is a method of inhibiting the crystallization of nanoparticles and/or dispersing nanoparticles, and compositions comprising crystallization inhibited nanoparticles and/or dispersed nanoparticles.