A method for improving the mechanical hardness of polymer particles is provided, the method comprising subjecting the polymer particles to a thermal cycle of heating and subsequently cooling. The method is applicable for use with combinations of preferably three monomers, the monomers having hydrophilic and hydrophobic groups in their polymer chain in order to achieve preferential orientation of the polymer chains in a polar solvent after applying the heating cycles of the invention (for example, but not limited to, polymethylmethacrylate and polystyrene based terpolymers and copolymers). Polymeric abrasives used in slurry compositions for polishing copper and their use in a chemical mechanical polishing method are also provided.