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 usi ng 2,5-bis(2-thia-3-butenyl)-1,4-dithiane (TBD) with a radical initiat or for an optical polymer having a high refractive index (n(D)) and Ab be number (nu). Homopolymerization of TBD (72.9% conversion) and copol ymerization with acrylonitrile or acrylates having nonpolar groups (50 .4-81.3% conversion according to the comonomers used) in a limited com position range yielded hard and transparent polymers suitable for appl ication in optics. The methacrylates used yielded no polymeric product as a result of the copolymerization. The obtained polymers had T-g, n (D) and nu ranging between 41.0-124.0 degrees C, 1.678-1.546 and 34.1- 43.8, respectively, except that poly(TBD) did not exhibit T-g below 20 0 degrees C, and it had the highest n(D). Most of the polymers have hi gher n(D) and nu 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 n(D) and nu ar e discussed based on the Q-e scheme and on the Lorentz-Lorenz equation , respectively. This work shows that TBD serves as a useful material f or the preparation of polymers having high n(D) and nu along with a T- g of more than 100 degrees C, and that the polymers thus obtained are promising optical materials.