In this paper a methacrylic derivative of naphthalene-2-thiol – S-naphthalene-2-yl 2-methylprop-2-enethioate (2-NAF-S-Met) was synthesized and then copolymerized with two monomers of industrial significance, i.e. methyl methacrylate (MMA) and styrene (ST). The thermal properties of the copolymers were investigated by differential scanning calorimetry (DSC) and thermogravimetry (TG/DTG). Also, Shore hardness tests of the obtained polymers and optical properties (transparency) were assessed. By replacing the thioester-linked substituent components of the side chains in the thioester-derived polymers through the thiol-thioester exchange reactions, a facile control over the polymer properties (hardness, Mn and Mw, transparency, stability, solubility, etc.) was demonstrated. The molar masses (Mn) of new materials after thiol-thioester exchange using 2-mercaptoethanol were reduced to 6.85 × 104 Da (for ST copolymers) and to 1.22 × 106 Da (for MMA copolymers), respectively. Second exchange sequence with thiophenol resulted in an increase in the molar mass of these products. The replacement of substituents also caused an improvement in thermal stability, especially for MMA copolymers, as well as a decrease of the glass transition temperatures.