Font Size: a A A

Study On The Reaction Mechanism Of Ultraviolet Light Promoting The Gelation Of Organosiloxane And The Preparation Of Rare Earth Luminescent Glass

Posted on:2015-01-03Degree:MasterType:Thesis
Country:ChinaCandidate:Y WangFull Text:PDF
GTID:2271330431497641Subject:Polymer Chemistry and Physics
Abstract/Summary:PDF Full Text Request
The family of organotrialkoxysilanes RSi(OR’)3represents a class of versatile building blocks toward designing silicon-based hybrid organic-inorganic materials, which have been widely used in medical science, chemical engineering, national defense military and electron optics and other fields. The sol-gel process of organo-trialkoxysilanes always needs a long time however, which limits the further use of the method. Thus prompting of sol-gel process becomes a problem urgently to be solved in the preparation of the gel material. So far, a variety of reaction factors have been adjusted to shorten the sol-gel process, including pH of the sol-gel system, reactive temperature, the proportion of Si/water, co-solvents and crosslinking agent and so on. In the1990s the researchers found that the ultraviolet radiation can accelerate the sol-gel process of TEOS. The reason was speculated that ultraviolet irradiation caused-OH in the hydrolysis and condensation of organotrialkoxysilanes, which enhanced the gel formation. In our previous work,-OH induced by Fen ton agent was also found to promote the sol-gel process., but, the introduction of Fe2+inevitably affects the purity of the materials. Given the potential value of rapid, simple, green, low-temperature technological process in industrial production and the applications, our research is mainly focused on the field of UV radiation promoting sol-gel process of organotrialkoxysilanes. Reviewing all the literatures at home and abroad, there are still some important problems need to be solved:(1) The systemic research of UV-radiation effect on sol-gel process is still unavailable, and the molecular mechanism in detail is not clear.(2) For bifunctional organotrialkoxysilanes, the interplay between organic polymerization and inorganic condensation is still an open problem.(3) The process of employing bifunctional organosiloxane to prepare sol-gel materials needs to be exploited, especially in the application of synthetizing rare earth-ormosil hybrid luminescent material. At present, rare earth elements are dispersed in gel matrix via physical doping or embedding. In such a way, the luminous efficiency was diminished due to heterogeneous dispersion or surface leakage of the entrapped rare earth. To solve the above problems, we make a series of scientific research and exploration, and the specific content and experimental conclusions are described below: (1) In this work, the FT-IR and other technologies were used to study the influence of UV-radiation and Fenton agent induced-OH on the gelation process of different sol-gel system, and the molecular mechanism on UV-radiation effect on sol-gel process was studied systematically. The fluorescence spectra and UV absorption spectra were employed to study the influence about the ultraviolet irradiation caused·OH and·OH induced by Fenton agent on sol-gel process. The results indicated that the sol-gel process of organotrialkoxysilanes can be promoted by introducing·OH, at the same time, UV-radiation also can accelerate the gelation process of organotrialkoxysilanes. Moreover, this effect gradually increases with increase of·OH and ultraviolet irradiation, in other words, they have the equivalence. The fluorescence spectra and UV/vis absorption spectra also showed that UV-radiation can produce·OH, and ultraviolet irradiation caused·OH in the hydrolysis and condensation of organotrialkoxysilanes. In conclusion, the essential key of ultraviolet radiation prompting sol-gel process is·OH formation.(2) In this study, the interplay between organic polymerization and inorganic condensation of MAPTMS and GPTMS were respectively traced by FT-IR and29Si NMR. At the same time, video optical contact angle measuring instrument, light transmittance measurement instrument, scanning electron microscope (SEM) were also used to test the property of the thin films obtained from MAPTMS. The competition of organic polymerization and inorganic condensation was investigated under different conditions. The same researches have been done to the GPTMS as above. The results show that the Si-O-Si network forming inhibits the C=C polyreaction of MAPTMS. And the inhibition was enhanced along the extension of hydrolytic condensation time. The29Si NMR spectra show that the products have different Si-O-Si structure in different aging times. At the early stage, C=C polymerization is little influenced by Si-O-Si backbone network under natural condition. Under UV radiation, however, the C=C polymerization is greatly influenced by Si-O-Si formation because the polymerizate is incompatible with water. The sol-gel material of MAPTMS can achieve rapid solidification under UV radiation via synchronous organic polymerization and inorganic condensation. In such a way, the thin organic-inorganic interpenetrating network films were obtained quickly. The UV curing materials have the properties of good hydrophobicity, thermal stability and excellent optical performance, without obvious cracks, defects and crease. The GPTMS also has obviously inhibition between organic polymerization and inorganic condensation on each other in sol-gel process. In particular, ring-opening is significantly limited by the Si-O-Si network forming. The inhibition-interplay between epoxy group polymerization and inorganic condensation of GPTMS was demonstrated by FT IR under thermal polymerization.(3) Based on the above work, the3-methacryoxypropyltrimethoxysilane (MAPTMS) and acrylic europium Eu(AA)3were used to produce fluorescence gel glass. Different from the traditional way of physical doping, covalent bonding (polymer copolymerization) was adopted to introduce rare earth. This work provides a new method to create new hybrid luminescent material and in the process is a combination of physical dispersion and chemical bonding to rare earth metal ions. The optical properties and fluorescence luminous efficiency of rare earth bonded fluorescent gel glass were revealed by fluorescence spectrophotometer and ocean optics ultraviolet visible near infrared spectrometer. The results showed that the fluorescence gel glass have good fluorescence efficiency and optical performance.
Keywords/Search Tags:Organically modified siloxane, sol-gel process, UV radiation, free radical, bifunctional polymerization
PDF Full Text Request
Related items