Design, Synthesis And Properties Of Organosilicon Polymeric Free-radical UV-photoinitiators

Light-curing technology has been widely used in coatings, adhesives, inks and other fields. Along with the expanding of its application areas and the increasing requirements for environmental protection, it attracts more and more attention of researchers. As the key component of the photo-curable formulation, the photo initiators are capable of generating reactive center under light such as free radical, cation, anion, etc., to initiate the polymerization of substances. With the development of light-curing technology and the requirements of environment protecting, it is important to research and develop macromolecular and water-borne photo initiators for reducing toxic and expanding the usage of UV curing technology. Organic silicon is a kind of inorganic-organic hybrid material which has series of excellent properties such as excellent weather resistance, water resistance, physiologically inert and very excellent surface properties. It can give a number of new properties to photo initiators by introducing silicone to the molecular designing. In this thesis, we designed and synthesized a series of organic silicon free radical UV photoinitiators based on the organic silicon compounds. The main contents are described as follows:Chapter one reviewed the classification, mechanism and research trends of photoinitiators, highlighted the existing organic silicon photoinitiators. The design ideas and research content was proposed based on the current needs.In the second chapter, a kind of waterborne polysilane photoinitiator polysilane-co-poly(polyethyleneglycol acrylate) P-3which could easily dispersed in water was prepared by an efficient photodecomposition of polymethylphenylsilane in the presence of acrylate functionalized polyethyleneglycol. The structure of P-3was characterized by NMR, IR and UV spectroscopy, and the polysilane and polyether segments were found in P-3. The polysilane in P-3could cleavage under UV irradiation by the study of real-time IR and real-time UV spectroscopy. P-3could be effective to initiate the polymerization of acrylamide, acrylic acid and hydroxyethyl methacrylate in aqueous solution. The initiation rates of two different polysilane weight content of polysilane-polyether copolymer P-3-1and P-3-2were studied by of the real-time IR spectrum. The results showed that after60seconds’ irradiation of30mW/cm2UV intensity,1%of initiator concentration, P-3-1and P-3-2initiated the double bond conversion of20%aqueous solution of acrylamide reached to60%and70%, respectively. P-3was a kind of novel aqueous photoinitiator with greater potential which has high initiator efficiency and was easy to synthesize.In the third chapter, we designed and synthesized small molecule photoinitiators substituted hyperbranched polysilanes BP-PS, TX-PS, BTP-PS and Flu-PS and all of them were macromolecular photoinitiators. The structures of them were determined by NMR and IR. The UV spectral studies show that these substituted hyperbranched polysilanes can improve the utilization of UV light, especially far ultraviolet light, of hyperbranched polysilane. Real-time IR spectroscopy studies showed that these substituted hyperbranched polysilanes UV initiator efficiency were higher than that of unsubstituted hyperbranched polysilane Bu-PS. The results showed that after less than10seconds’ irradiation of30mW/cm2UV intensity,1%of initiator concentration, all the substitued.hyperbranched polysilanes initiated the double bond conversion of HDDA more than90%showed that all these substituted hyperbranched polysilanes were efficient photoinitiators. The ESR studies showed that, BP-PS and TX-PS could both generate silicon radicals by cleavage and generate carbon radical by hydrogen abstraction reaction. Substituted hyperbranched polysilanes overcomed the disadvantages of small molecule photoinitiators, meanwhile, all of them were efficient photoinitiators with good potentials of applications.In the fourth chapter, we synthesized the polysilane-silicon resin hybrid materials P-2based on hydrolysis of the Si-Cl bond containing hyperbranched polysilane in the third chapter and chlorosilane monomers. The structures and physical properties were characterized by NMR, FT-IR, UV-vis, GPC, DSC and TGA. Real-time UV spectra studies showed that the hybrid materials retain the optical properties of polysilane which could cleavage under UV light. The polysilane-silicon resin hybrid materials were liquid form at room temperature because of the structure of silicone resin and have good dissolution properties which would broaden the use of polysianes. Real-time IR studies showed that the hybrid materials still have a good performance as UV initiators which were very effective free radical photoinitiators. The real-time IR results showed that after less than20seconds’irradiation of40mW/cm2UV intensity,1%of initiator concentration, all the hybrid materials initiated the double bond conversion of HDDA more than90%. The UV-vis, XPS, surface contact angle, and TGA were employed to study the surface properties of the hybrid materials which showed that the materials tend to enrichment to the surface cause of the low surface energy properties of the hybrid materials. The contact angle tests showed that the contact angle was raised from72.7°to109.2°by addition of5%mass amount of P-2-3in poly-hexanediol diacrylate film. These polysilane-silicon resin hybrid materias not only retain the properties of polysilane as UV initiatory but also have excellent properties of silicone resin. In addition to light-curing, they may also modify the cured products which makes them as a new kind of multi-functional UV initiator.In the fifth chapter, the benzophenone functionalized silicone resin BP-Si-resin was prepared by reacting4-hydroxy-benzophenone hydrolysis sodium salt with silicone resin prepolymer containing Si-Cl bonds which was prepared by hydrolysis of chlorosilane monomers. BP-Si-resin was a macro molecular UV photoinitiator which was a viscous liquid at room temperature and has excellent solubility and capability in prepolymer. The structures and physical properties were characterized by NMR, FT-IR, UV-vis, GPC, DSC and TGA. The real-time IR tests showed that BP-Si-resin had a high UV initiation rate. The rate of4%mass amount of BP-Si-resin initiated the polymerization of HDDA was close to which by1%mass amount of BP. UV spectroscopy, TGA, and XPS studies directly or indirectly proved that BP-Si-resin was tend to enrichment in the surface of the solution, indicating that BP-Si-resin also has the low surface energy properties of silicone resin. The contact angle tests showed that the contact angle was raised from72.7°to118.3°by addition of10%mass amount of BP-Si-resin in poly-hexanediol diacrylate film. This feature of BP-Si-resin could make the cured products surface have better hydrophobicity, weather resistance, resistance to radiation and other advantages, making BP-Si-resin as a macromolecular organosilicon UV free radical photoinitiator having surface modified function.