2,2＇-Mercaptoethylsulfide dimethacrylate (MESDMA) was synthesized from 2,2＇-mercaptoethylsulfide (MES) by a Phase-Transfer Catalysis technique and, was characterized and corroborated by H-1-NMR and FTIR spectra. Except for the poor impact strength, the MESDMA homopolymer resin shows better comprehensive properties, such as a higher refractive index (1.625), lower dispersion (Abbe＇s number 36), and good heat-resistance (T-g 150 degrees C) and surface hardness (3H), etc. Copolymerizing with styrene (St) can modify most of the properties of the resin. The refractive index, Abbe＇s number, onset wavelength, density, water-absorption ratio, and absorption intensity of peaks in NIR region, etc, all display a regular change along with the proportion of MESDMA/St. The main absorption peaks in NIR region are assigned as follows: 1680 (first overtone) and 1144 nm (second overtone) to the phenyl C-H vibration of polystyrene; 1694 nm (first overtone) to nu(CH3); 1730 and 1750 nm (first overtone) to nu(CH2) for ordinary CH2 and for CH2 connected with S or COS groups, respectively; and 1186 nm (second overtone) to aliphatic C-H vibration. The prominent advantage achieved by copolymerization is that the impact strength can be improved as much as 10-fold at a proper composition of the monomers (75% St). (C) 2000 John Wiley & Sons, Inc.