Sulfur-Rich Polythiol\nResin Based on Polyalkylene\nSulfides: Peculiarities of Preparation and Properties of the Cross-Linked\nMaterials

Preparation\nof polyalkylene sulfides bearing a latent thiol functionality\nvia ring-opening copolymerization of propylene sulfide and dithiocarbonate-functionalized\nepisulfide (<i>O</i>-isobutyl <i>S</i>-(thiiran-2-ylmethyl)\ncarbonodithioate, ETiBX) was demonstrated. Potassium <i>O</i>-methyl xanthate in complex with 18-crown-6 ether PMX[18C6] was used\nas an activator of the polymerization process. In contrast to polymerization\nof propylene sulfide, the process associated with (co)polymerization\nof ETiBX was found to be complicated by the pronounced chain transfer\nreaction. It was shown that copolymerization of propylene sulfide\nwith even as low as 1 mol % of ETiBX leads to a dramatic decrease\nin the <i>M</i><sub>n</sub> of the resulting polymer (from\n117 to 17.8 kg/mol) accompanied by the distinct multimodality of the\ncopolymers obtained. Consecutive aminolysis of thus obtained copolymers\nbearing xanthate groups provided SH-functionalized polyalkylene sulfides\nas a viscous resin, which allows one to perform multiple possible\npathways for the subsequent modification of the synthesized polythiols.\nThe obtained polythiols were tested as UV-curable one-component (solvent-free)\ncompositions to prepare the first generation of cross-linked polyalkylene\nsulfides. Thus, the prepared transparent elastomers show a relatively\nhigh refractive index close to 1.6 and enhanced thermal properties\nin terms of glass transition and the onset of thermal degradation\ncompared to high-molecular-weight polypropylene sulfide. The tested\norganogels show high swelling ratios in toluene, tetrahydrofuran,\nand chloroform. The highest swelling ratio was determined for the\norganogel cross-linked with triallyl isocyanurate and soaked in chloroform\n(614%).