Novel Photosensitive Thio-Containing Polyurethane as Macrophotoinitiator Comprising Side-Chain Benzophenone and Co-Initiator Amine for Photopolymerization

A novel thio-containing polyurethane (PU) as macrophotoinitiator (PUIA) was synthesized through polycondensation of 3,5-diamino-4‘-thiophenylbenzophenone (DATBP), hexamethylene-1, 6-diissocyanate (HDI), and N -methyldiethanolamine (MDEA). The beznophenone and co-initiator amine structures were successfully introduced into the backbones of PUIA. A macrophotoinitiator without co-initiator amine in polymer chain (PUI) and a macroamine (PUA) were also synthesized for comparison. FT−IR, 1 H NMR and GPC analyses confirmed the structures of all polymers. The UV−vis spectra of PUIA and PUI are similar and both exhibit the maximal absorption near 320 nm. ESR spectra indicate PUIA can efficiently generate free radicals. The photopolymerization of trimethylolpropane triacrylate (TMPTA) and PU prepolymer, initiated by PUIA, PUI/MDEA, PUI/PUA, DATBP/MDEA, and DATBP/PUA, was studied by photo-DSC. The results show that PUIA is the most efficient photoinitiator for both TMPTA and PU prepolymer. As for the polymerization of PU prepolymer, the final conversion is higher than 97%.