SULFUR-CONTAINING POLYACRYLATES .4. THE EFFECT OF S-LINKAGE AND O-LINKAGE ON THE PHOTO INDUCED AND THERMALLY-INDUCED POLYMERIZATION OF DIMETHACRYLATES

The photo- and thermally induced polymerization of four analogous dime thacrylates-2,2'-thiobisethanol dimethacrylate, 2,2'-oxybisethanol dim ethacrylate, pentanediol-1,5-dimethacrylate, and butanediol-1,4-dimeth acrylate-was studied to determine the influence of - S - and - O - lin kages on the polymerization course. Generally, the presence of the het eroatom in the monomer molecule results in higher reaction rates and y ields but the extent of this influence highly depends on the polymeriz ation conditions and the type of heteroatom. The effect of the thioeth er bond exceeds the effect of the ether bond at lower (40-degrees-C) t emperature in the presence of oxygen but the reverse situation takes p lace at higher (75-degrees-C) temperature and/or in an inert atmospher e when photofragmentating and thermal initiators are used. The results are discussed mainly in terms of propensity of sulfides and ethers to act as hydrogen donors and chain-transfer agents. (C) 1993 John Wiley & Sons, Inc.