Study On UV-LED Light Initiated Thiol-ene Photo Click Reaction

The thiol-ene photo click reaction has become a focus of research in recent years owning to its high efficiency, rapidly, high selectivity, mild reaction conditions, high yield and ease of implementation. This paper is divided into three parts to introduce it.1. The Synthesis of Polyfunctional Castor Oil-based Polyurethane Acrylate by the Auxiliary of Thiol Photo Click ReactionThis thesis synthesized castor oil-based polyol(COME) via thiol-ene photo click reaction, then COME was modified by isocyanate polyurethane reaction with hydroxypropyl acrylate(HPA), isophorone diisocyanate(IPDI) and PEG as the chain extender in order to prepare the polyfunctional castor oil-based polyurethane acrylate(COME-PUA).Structures of the products were characterized by 1HNMR and FT-IR. Results confirmed the expected structure. Furthermore, photopolymerization properties of COME-PUA were revealed by real-time Fourier transforminfrared(RTIR) spectroscopy at room temperature, and compared with common castor oil-based polyurethane acrylate(CO-PUA), the photopolymerization of polyfunctional COME-PUA showed a higher R pmax with 854 min-1 soon after the beginning(0.098 min), and 80% yield was obtained in the shorter irradiation time(0.195 min). Whereas CO-PUA has lower photo-initiated activity, and gave the lower R pmax(662 min-1), resulting in 80% conversion in 0.260 min. Furthermore, some physical properties of curing films were studied, showing good thermal stability, adhension and hardness.2. Study on synthesis and UV-LED photopolymerization of thioxanthone dicarboxamide derivativesBecause UV-LED(UV Light Emitting Diodes) photopolymerization has many significant advantages, so it is current trend to replace traditional mercury lamp, but photoinitiators for UV-LED photopolymerization still remain rare, this chapter studied photopolymerization properties of three thioxanthone dicarboxamide derivatives in UV-LED exposure via monitor the conversion of-C=C of TPGDA by Real-time FTIR. Results showed those thioxanthone dicarboxamide derivatives had perfect free radical activity in UV-LED light, the maximum polymerization rate is up to 328.1%, and final conversion could reach more than 95% within 6 min. Therefore, these derivatives could be used as photoinitiator in UV-LED photopolymerization system. Based on safety, strong penetration ability of UV-LED initiation and combined with the theoretical study on thioxanthone dicarboxamide derivatives before, the application space of thiol-ene reaction is expected to expand greatly.3. Thiol-ene Michael addition reaction controlled by phototriggered base proliferationFree radical reaction of thiol-ene photo click reaction is not ideal click chemistry type, there is monomer homopolymerization and low monomer conversion existing, and uncontrollable, it is difficult to obtain the target product. Therefore, this charpter intended to introduce the phototriggered base proliferation and UV-LED photopolymerization into thiol-ene reaction. we synthesized photobase generator 2-(2-nitrophenyl) propyloxycarbonyl-hexylamine(NPPOC-HA) and amine amplifier 1-(9- fluorenylmethoxycarbonyl) hexylamine, NPPOC-HA has UV absorportion above 300 nm, and photolysis products are amine and styrene, no free radical produced. Furthermore, amine proliferation in solution was investigated. Next, we used phototriggered amine proliferation initiated via UV and UV-LED respectively to control the thiol-ene click reaction, reducing the side effects. RTIR was adopted to monitor the infrared absoption peaks change of-SH and-C=C, integrating the peak area to verify the equal proportion reaction of thiol-ene. UV-LED phototriggered base proliferation reaction, which integrated the safety and strong penetrating ability of UV-LED photopolymerization as well as Domino free radical photopolymerization based on phototriggered base proliferation reaction, is expected to expand the application of thiol-ene click reaction.