Study On Synthesis Of Organosilicon Macromolecular Photoinitiator And Initiating Gradient Polymerization

Photopolymerization science and technology has drawn considerableattention for various industrial applications in the past decades. Thephotoinitiator plays a key role in the photopolymerization process, so muchresearch has been focused on preparing some photoinitiators with newdesirable properties. In this paper, based on the lower surface energy andtension of organosilicon, a variety of organosilicon macromolecularphotoinitiators was synthesized, which had good ability to self-float up,leading to spontaneously forming the photoinitiator concentration gradientin the photopolymerization system and the enrichment of the photoinitiatoron the surface of the system. In this way, the molecular weight gradientmaterials could be obtained by controlling concentration distribution oforganosilicon macromolecular photoinitiator. The method has theadvantages of being rapid, convenient, controlled and environmentallyfriendly due to combining features of photopolymerization and silicone.Meanwhile, the enrichment of the photoinitiator on the surface of thephotopolymerization system could effectively mitigate inhibition of oxygen in radical photopolymerization, providing a new method to improvematerial surface properties and regulate micromorphology. The study couldprovide the theory and technology basis for application of organosiliconmacromolecular photoinitiators and broaden its application fields.The study work and conclusions are described as follows:1. Two kinds of abstracting hydrogen type organosiliconmacromolecular photoinitiators HBP-Si-A/X were synthesized basing ontraditional photoinitiator4-Hydroxybenzophenone (HBP) and polysiloxane.Their structures and properties were investigated by FTIR,¹H-NMR, GPC,UV absorption, RTIR, XPS, SEM and EDS. The UV absorption spectrashowed that HBP-Si-A/X had maximum absorption peak at290nm and255nm respectively. The kinetics of photopolymerization initiated byHBP-Si-A indicated that it was effective photoinitiator and could initiatephotopolymerization. It had good ability to float up due to the lowersurface energy and tension of organosilicon. As a result, the HBP-Si-Acould easily form concentration gradient in a photopolymerization systemand initiate gradient photopolymerization to obtain molecular weightgradient materials. The enrichment of HBP-Si-A on the surface of thesystem could more obviously mitigate inhibition of oxygen in radicalphotopolymerization.2. Three kinds of abstracting hydrogen type organosiliconmacromolecular photoinitiators (HBP-Si-A/B/C) with different silicon content were synthesized basing on traditional photoinitiator HBP andepoxy polysiloxane. Their structures and properties were investigated byFTIR,¹H-NMR, GPC, UV absorption, RTIR, SEM and contact anglesmeasurement. The UV absorption spectra showed that HBP-Si-A/B/Cpossessed a similar maximum absorption peak at290nm. The kinetics ofphotopolymerization initiated by HBP-Si-A/B/C indicated that they wereeffective photoinitiators and could initiate photopolymerization.HBP-Si-A/B/C with different silicon content had different ability to floatup. As a result, the gradient polymer with more significant molecularweight gradient could be obtained by using the polysiloxane benzophenonephotoinitiator with higher silicon content, which had better ability to floatup caused by lower surface tension and energy, and the surface propertywas connected with the surface microstructure. In addiation, the increase ofsilicon content in the polysiloxane-based photoinitiator could decrease thedispersion surface energy of gradient polymer film initiated by it andgenerate a more hydrophobic surface by the change of microstructure. Theenrichment of HBP-Si-A/B/C on the surface of the system could moreobviously mitigate inhibition of oxygen in radical photopolymerization,leading to the changes of micromorphology.3. Three kinds of cleaving type organosilicon macromolecularphotoinitiators (NH₂-2959-2, NH₂-2959-4, NH₂-2959-CC) weresynthesized basing on traditional photoinitiator2-hydroxy-2-methyl- p-hydroxyethyletherpropiophenone-1(2959), amino polysiloxane andp-toluenesulfonyl chloride. Their structures and properties wereinvestigated by FTIR,¹H-NMR, GPC, UV absorption, RTIR, XPS andSEM. The UV absorption spectra showed that NH₂-2959-2,NH₂-2959-4,and NH₂-2959-CC possessed a similar maximum absorption peak at275nm. The kinetics of photopolymerization initiated by NH₂-2959-2,NH₂-2959-4, and NH₂-2959-CC indicated that they were effectivephotoinitiators and could initiate photopolymerization. They had goodability to float up due to the lower surface energy and tension oforganosilicon. As a result, they could easily form concentration gradient inphotopolymerization system and initiate gradient photopolymerization toobtain molecular weight gradient materials. However, their ability to floatup was weaker than abstracting hydrogen type organosiliconmacromolecular photoinitiator HBP-Si-A. Therefore, the degree ofinitiating gradient photopolymerization was less significant than HBP-Si-A.Their enrichment on the surface of the system could only mitigateinhibition of oxygen to some extent in radical photopolymerization.Comparing with abstracting hydrogen type organosilicon macromolecularphotoinitiator HBP-Si-A, HBP-Si-A had stronger ability to mitigateinhibition of oxygen.