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Ultraviolet organic modified siloxane Sol-Gel process

Author: LiWei
Tutor: HuDaoDao
School: Shaanxi Normal University
Course: Polymer Chemistry and Physics
Keywords: Organosiloxane Sol-Gel process Hydrolysis - condensation reaction UV radiation Radicals
CLC: TB322
Type: Master's thesis
Year: 2010
Downloads: 53
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Abstract

Organosiloxane organic - inorganic hybrid materials synthesis field in a class of important precursor. Hydrolysis - condensation reaction occurs under different conditions, by the sol - gel process can be prepared by a variety of structures different, performance, a variety of hybrid materials. Such hybrid material is stable because of its chemical properties, optical transparency, and the superiority of the mechanical properties and are widely used in the field of optical devices, electronic components, biomedical sensor, catalytic, functional coating film, etc., is the materials science today one of the hot areas of research. While it found that ultraviolet radiation in the sol - gel process using siloxane prepared organic - inorganic hybrid materials, there are many advantages of conventional heat treatment, for example, rapid curing, room temperature operation, low energy consumption, pollution small, and the product structure and performance is more excellent. Through traditional sol - gel materials prepared in the latter part of the drying and heat treatment process, the condensation is affected defects resulting product performance, light treatment under the same conditions can effectively avoid or reduce this defect. However, most of the ultraviolet radiation of the siloxane sol - gel process studies are concentrated in materials syntheses, and most researchers believe that light can promote siloxane hydrolysis and condensation reaction, causing the organic groups photolysis so structural rearrangement of its occurrence. However, the mechanism of research is not yet conclusive. Meanwhile, in a double bond-containing polymerizable organosiloxane, more emphasis photosensitizers in the presence of organic photoinitiator end ethylenically polymerizable UV radiation hydrolysis - condensation reaction of the inorganic end impact, but often overlooked. Propyl methacrylate containing polymerizable olefinic bond trimethoxysilane (3-Methacryloxypropyltrimethoxysilanesilane, MAPTMS) widely used in view of the organic end intended by its hydrolysis under UV irradiation with light conditions - the comparative study of the condensation reaction, discloses UV organosiloxane hydrolysis - condensation reaction mechanism. These findings will undoubtedly controllable synthesis of synthetic conditions and materials are optimized hybrid materials have important theoretical significance and application value. In view of this, this thesis conducted the research work of the following two parts: first, methyl acrylate, propyl trimethoxy silane, octyl trimethoxy silane and trimethoxy silane three typical organosiloxane as precursor using a fluorescent probe technology, means of ATR-IR, 1H NMR, 13C NMR and 29Si NMR contrast to online tracking three precursor under UV irradiation with light conditions hydrolysis - condensation reaction. Fluorescent probe experiments: The results show that compared with the non-lighting system, and pyrene in the organosiloxane containing hydrophobic substituents Hydrolysis - condensation system yl stimulated association complexes fluorescence peaks in the reaction to pre-clear and rapid growth, while the late waning. The results indirectly indicate that ultraviolet promote hydrolysis and condensation reaction. FTIR results show that the: UV irradiation organosiloxane system, the characteristic peaks of the Si-OH reactive pre late characteristic vibration of Si-O-Si peaks significantly increased significantly increased reaction time. UV irradiation conducive to hydrolysis and condensation reaction. Si related species 29Si NMR results show that: the hydrolysis and condensation reactions of the non-lighting system is almost accompanied occur, thus formed mainly linear Si-O-Si chains, the crosslinked product is relatively small. From the macroeconomic performance of the system, even if the system reaction a few months or even a year despite the increase in viscosity, but did not find the gelling phenomenon. In contrary, the illumination system so that the characteristic signal of the crosslinking Si species increased significantly, and in macroscopic gelling exhibit short time. Meanwhile, a polymerizable double bond-containing MAPTMS system detection results of the infrared spectroscopy showed that: No significant change in the UV radiation, the double bond in the molecule thereof. Thermal analysis results also from the side that organic substituent is not obvious decomposition occurs. The results of the study show that: the role of ultraviolet radiation on organic the siloxane hydrolysis - condensation reaction occurs mainly in inorganic end. Its main features are: UV radiation can promote the reaction of hydrolysis of the precursor is more completely formed easily crosslinked species, eventually leading to the system gelling of the organosiloxane. Second, the correlation between the study of ultraviolet radiation on organic the siloxane hydrolysis - condensation reaction with free radicals. Fenton reaction system can make available hydroxyl radicals organosiloxane difficult gelled gelling in a very short time, and forming a hard, transparent material, the results show: the hydroxyl radical having promote siloxane sol - condensate gelling of the colloidal system; ultraviolet radiation containing the strong fluorescence characteristics of the Ce3 the MATPMS hydrolysis - condensation system, the fluorescence intensity was significantly reduced, and the results show that: with fluorescent properties of Ce3 oxidation of non-fluorescent properties of Ce4. Ultraviolet radiation system containing oxidizing radical; when the system presence of radical scavengers epinephrine gel effect of UV irradiation system is significantly hampered, the above experimental results indirectly proved UV promoting organosiloxane gelation of the system and its caused by the presence of free radicals associated. Ultraviolet radiation and free radicals siloxane Sol-Gel process with a certain degree of equivalence. In this study, the work of the ultraviolet radiation to promote explore the mechanism of organically modified siloxane Sol-Gel process provides valuable information.

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