Synthesis and cationic photopolymerization of a difunctional episulfide monomer

Sulfur-containing compounds have attracted many interests in the UV curing field. A new episulfide monomer, 1,4-butanediol episulfide (BDDGE-PSTC (BPT)), was synthesized via replacement of the oxygen atoms in 1,4-butanediol diglycidyl ether (BDDGE) with sulfur atoms. Its structure was confirmed by FTIR, 1H NMR and ESI/MS. The photopolymerization kinetics of BPT was studied by real-time infrared spectroscopy (FTIR), under conditions with different photoinitiator concentration and type, atmosphere and so on. Physical properties such as refractive index and adhesion strength of the cured BPT polymer were studied. It was found that the cured BPT polymer showed higher refractive index and better adhesive strength on polyethylene terephthalate (PET) and iron in comparison with BDDGE. Thermal and mechanical properties of UV-curing BPT films were also investigated by TGA and DMA.

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► Difunctional episulfide (BPT) was successfully synthesized.
► The reactivity of BPT was higher than that of BDDGE (about 25 μm film).
► The cured BPT had higher refractive index compared to BDDGE.
► BPT polymer had better adhesive strength on PET and iron than that of BDDGE.