Polymer International zyxwvutsrq 24 (1991) 179-184 Sulphur-Containing Polyacrylates. 111 zy : UV-Induced Copolymerization of Methyl Methacrylate with some Dimethacrylates Containing Ether or Thioether Linkage? Ewa Andrzejewska Poznan Technical University, Institute of Chemical Technology and Engineering, P1.Sklodowskiej-Curie 2, 60-965 Poznan, Poland (Received 13 November 1989; revised version received 21 March 1990; accepted 3 April 1990) Abstract: The UV-induced copolymerization of methyl methacrylate (MM) with 2,2’-thiobisethanol dimethacrylate (TEDM) and MM with 2,2’-oxybisethanol dimethacrylate (OEDM) was investigated for a wide range of the diester content (6-80mol%) in the initial mixture. The influence of the feed composition on the course of copolymerization .was determined. It was found that there exists a minimum on the plot of maximum yield of soluble copolymer versus diester content at a diester content of 30 mol%. The total copolymer yields were lower in the case of mixtures containing TEDM comonomer. Determination of the reactivity ratios gave the following values: for MM + TEDM zyxwvut r, = 0.21, zyxwv rb = 4.59 and for MM + OEDM ra=055, r,=4.42. A possible explanation of the results obtained is discussed. Key words: methyl methacrylate, 2,2’-thiobisethanol dimethacrylate, 2,2‘- oxybisethanol dimethacrylate, crosslinking copolymerization, UV-initiation, monomer reactivity ratios. zyxwvuts I NTRODUCTlON co-~orkers~’~ described two extreme cases of network formation, occurring at low and high It is well known that free radical copolymerization concentrations of the crosslinking agent respec- of monounsaturated and biunsaturated com- tively. In the first case the competitive reactions of onomers leads to network formation. Before gel- intermolecular and intramolecular crosslinking ation a soluble copolymer is formed which can then proceed slowly until the gel point is reached. The undergo intra- and intermolecular crosslinking. networks produced resemble relatively homogen- According to Lubashevskii & Obukhov’ there exist eous structures with a few dangling ends and some two different regimes of gelation depending on the crosslinks wasted in elastically inactive cycles. In the ratio of concentrations of bifunctional and tetra- second case, compact internally crosslinked mole- functional monomers and an initiator. The gel is cules resembling microgel particles are formed at the formed either after contact of the growing coils of primary stage. The cyclizations proceed rapidly until linear macromolecules, or as a result of essential the pendant vinyl groups inside microgel particles overlapping of growing macromolecules. Ishizu and are unable to react due to shielding effects. Network formation is achieved by the formation of inter- t Part I1 of this work appeared in Ref. El. molecular crosslinks among heterogeneous microgel 179 Polymer international 0959-8103/91/$03.50 zyxwvuts 0 1991 SCI. Printed in Great Britain