Poly(methyl methacrylate)-block-polysulfide-block-poly(methyl methacrylate) copolymers obtained by free-radical polymerization combined with oxidative coupling

Free radical polymerization of vinyl acetate in the presence of liquid polysulfides

“…of the thiocol and low molecular weight model mercaptans in the case of MMA and St polymerizations [10,11], which allows us to reasonably suppose that the same happens for VAc monomer, and therefore the C T of the thiocol terminal groups in VAc polymerization is very high, similar to that reported in the case of 2-mercaptoethanol. Therefore, the SH groups of the thiocol should be very rapidly consumed at the beginning of the polymerization, and as a consequence, their influence upon the process should be low.…”

“…The very low chain transfer constants of disulfides in the case of St and MMA indicate that there will be practically no insertion of these monomers within the thiocol chain during the free radical polymerization process, as previously demonstrated by us [10,11], while in the case of VAc polymerization extensive chain transfer reactions should occur because of the large C T , resulting in the incorporation of VAc units within the polysulfide chain with the formation of a new copolymer.…”

“…Thiocol (Akcros Chemicals GmbH, Thioplast G1) was used as received. Its SH group content, determined by iodometry [10] before the beginning of these experiments, was 0.497 mmol g À1 (1.64 wt.%), which corresponds to a number-average molecular weight (M n ) of 4020 g mol À1 , calculated assuming two SH groups/molecule.…”

“…Due to their relatively high reactivity, the SH end groups of thiocols served also as starting points for the preparation of various thiocol-based polymeric compounds like macromonomers and telechelics through polymer-analogous reactions [4,5], as well as block copolymers, by either polyaddition [6][7][8][9] or free radical polymerization [10,11] processes. In the last case, ABA triblock copolymers with polysulfide middle block and poly(methyl methacrylate) [10] or poly(methyl methacrylate-co-styrene) [11] side blocks were synthesized by taking advantage of both chain transfer ability in radical processes [12][13][14][15] and chemical oxidation sensitivity [16][17][18] of the mercaptan groups.…”

“…In the last case, ABA triblock copolymers with polysulfide middle block and poly(methyl methacrylate) [10] or poly(methyl methacrylate-co-styrene) [11] side blocks were synthesized by taking advantage of both chain transfer ability in radical processes [12][13][14][15] and chemical oxidation sensitivity [16][17][18] of the mercaptan groups.…”