Synthesis And Photochemical Application Of Visible Light Initiator Of Pyrrole

Photoinitiator is the key component of photopolymerization system.Under the irradiation of light source,it produces active species to initiate photopolymerization reaction.The traditional light source of photopolymerization is mercury lamp.However,due to the harm of mercury pollution to environment and biological safety,the use of mercury lamp is limited;Compared with mercury lamp,visible light emitting diode(LED)is more energy-saving and environment-friendly.Therefore,it is of great significance to develop photoinitiators with good initiation efficiency and absorption wavelength matching with LED visible light source.Pyrrolo[3,2-b]pyrrole is a 10-?electron heterocycle,which has superior photoelectric properties.The 10 electron structure has strong electron donating ability,and may produce different photochemical properties.Previously,1,4-bis(4-bromophenyl)-2,5-Bis(4-(nitro)phenyl)-1,4-dihydropyrrole[3,2-b]pyrrole was studied.It has initiating activity at UV wavelength.The substituent was replaced by nitro group to trifluoromethyl,which solved the problem that it can not be initiated under visible light,and it is a bifunctional radical initiator,The interaction between bifunctional initiator and acrylate monomer in photopolymerization system can be deeply studied,and it can also form a two-component system with other photoinitiators to play a synergistic role.It provides theoretical basis and experimental basis for the optimization of pyrrole photoinitiator in the future.(1)A bifunctional photoinitiator 1,4-bis(4-bromophenyl)-2,5-Bis(4-(trifluoromethyl)phenyl)-1,4-dihydropyrrole[3,2-b]pyrrole(PyBF)with pyrrole as mother nucleus was synthesized.The absorbance and mobility of initiator PyBF were tested by UV-Vis absorption spectrometer.It is found that its light absorption capacity is high,the absorption peaks are 256 nm and 368 nm,the maximum molar extinction coefficient is 333600 L·mol^-1·cm^-1,and its mobility is much lower than that of TPO initiator on the market.PyBF has excellent thermal stability,and the thermal decomposition temperature is above 340?.(2)Three different photopolymerization systems containing PyBF,PyBF/PEGDA,PyBF/TMPTA,PyBF/TPO/PEGDA and three comparative systems of PyBN/PEGDA,PyBN/TPO/PEGDA and TPO/PEGDA were studied.A two-component initiation system was formed with commercial initiator two phenyl(2,4,6-three methyl benzoyl)phosphine oxide(TPO).It was found that photoelectron transfer between PyBF and TPO could occur.Under the irradiation of 405 nm light source,when TPO and PyBF content ratio were 1:0.5,the synergistic initiation of PEGDA resulted in the highest gel rate approaching 100%.The surface shrinkage resistance of 0.5wt%PyBF/1wt%TPO/PEGDA component is the best.(3)The ability of PyBF/PEGDA and PyBN/PEGDA two system to form UV curable hydrogels was compared,and PyBN/PEGDA hydrogels were obtained.Hydrogel prepared by pyrrole photoinitiator is flexible and can withstand large strain.The hydrogel prepared by pyrrole photoinitiator is swelling controlled hydrogel.The fluorine-containing polypyrrole compounds designed and synthesized in this paper have broad application prospects in photosensitive materials,which provides a certain experimental basis for the design and synthesis of new efficient initiators.