Optical Polymer Having a High Refractive Index and High Abbe Number Prepared by Radical Polymerization Using 2,5-BiS(2-Thia-3-Butenyl)-1,4-Dithiane

Novel poly(vinylsulfide)s were prepared by addition polymerization using 2,5-bis(2-thia-3-butenyl)-1,4-dithiane (TBD) with a radical initiator for an optical polymer having a high refractive index (nD) and Abbe number (v). Homopolymerization of TBD (72.9% conversion) and copolymerization with acrylonitrile or acrylates having nonpolar groups (50.4–81.3% conversion according to the comonomers used) in a limited composition range yielded hard and transparent polymers suitable for application in optics. The methacrylates used yielded no polymeric product as a result of the copolymerization. The obtained polymers had Tg, nD and v ranging between 41.0–124.0°C, 1.678–1.546 and 34.1–43.8, respectively, except that poly(TBD) did not exhibit Tg below 200°C, and it had the highest nD Most of the polymers have higher nD and v than those of other conventional optical polymers and moreover, their values are comparable to those of flint glasses. The copolymerizability of TBD and the group contribution to nD and v are discussed based on the Q-e scheme and on the Lorentz-Lorenz equation, respectively. This work shows that TBD serves as a useful material for the preparation of polymers having high nD and v along with a Tg of more than 100°C, and that the polymers thus obtained are promising optical materials.