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化工，材料类都可以帮帮我阿
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下面是个句子，主要是说一种阳离子单体，我就是不知道，这个单体汉语到底是哪种物质，谢谢大家帮我一下^_^ the cationic monomer 2-(methacryloyl)ethyltrimethylammonium chloride (MTC) [ Last edited by wenwenstudy on 2009-4-10 at 09:27 ] |
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附件6 论文中英文摘要格式 作者姓名:陈敏 论文题目:聚合物/SiO2有机-无机纳米复合微球的制备与表征 作者简介::陈敏,女, 1978年6月出生,2003年8月师从于复旦大学武利民教授,于2006年6月获博士学位. 中 文 摘 要 近年来,有机-无机纳米复合微球的制备越来越受到人们的关注,这是由于这种有机-无机复合微球兼有有机材料和无机材料的优点,即通过调节两相的组分,尺寸和结构,可以得到兼具有有机相的易加工性和韧性以及无机材料的刚性,电性能与磁性能等特殊性能的复合材料.因此,这种复合微球的制备方法受到了广泛关注.本文通过无皂方法分别制备了草莓型或核-壳型的聚甲基丙烯酸甲酯(PMMA)/SiO2或聚苯乙烯(PS)/SiO2复合微球,并在研究复合微球的基础上,进一步采用一步法制备了无机二氧化硅空球.具体研究内容及结果如下: (1)以1-乙烯基咪唑(1-VID)为新辅助单体,在纳米二氧化硅粒子存在下, MMA与1-VID在水相中发生自由基共聚合,通过1-VID与纳米二氧化硅粒子表面显酸性的羟基之间的酸-碱相互作用,将有机-无机相结合起来,制备了在水相体系中稳定的具有草莓型结构的PMMA/SiO2复合微球.即有机聚合物颗粒表面吸附了大量纳米二氧化硅粒子,作为乳化剂对有机聚合物起稳定作用.整个制备反应过程中纳米二氧化硅粒子无需表面处理,且体系中无需另外加入乳化剂或助乳化剂.透射电镜和扫描电镜显示所得复合微球具有草莓型结构,且二氧化硅于表面富集.复合微球粒径介于150～330nm之间,热重分析表明复合微球中二氧化硅含量在15%～47%之间.复合微球中吸附的纳米二氧化硅的含量可以通过控制反应条件,如聚合反应温度,反应介质的pH值以及辅助单体1-VID的用量来调节. (2)利用未改性纳米二氧化硅粒子表面显负电性的性质,选用一种较为常见的阳离子单体——甲基丙烯酰氧乙基二甲基氯化铵(MTC),与MMA在水相中发生自由基共聚合,纳米二氧化硅颗粒通过电荷作用被吸附到有机颗粒表面并同时对有机颗粒起稳定作用,整个过程中无须另外加入乳化剂或者助乳化剂,纳米二氧化硅粒子也无须表面改性.透射电镜显示所得复合微球具有草莓型结构,且二氧化硅于表面富集.通过调节反应条件,可控制复合微球粒径在180～300nm之间,微球中二氧化硅的含量在16.4%～40.8%之间. (3)进一步采用无皂乳液聚合结合sol-gel的方法合成了以PS为核,SiO2为壳的复合微球,即首先用阳离子引发剂(AIBA),通过St的无皂乳液聚合制备了表面带有正电荷的PS微球.然后在乙醇/水介质中,二氧化硅前驱体正规酸乙酯(TEOS)在酸性条件下水解,形成的带负电性的二氧化硅与PS微球之间由于电荷作用而被吸附到PS微球表面,形成核-壳结构.壳层纳米二氧化硅的厚度(0～60nm)可以通过调节体系中TEOS浓度来控制.过程中PS微球无需表面处理,体系中也不用加入任何乳化剂或稳定剂.利用透射电镜(TEM),扫描电镜(SEM),ζ电势以及热失重(TGA)测试对所得到的杂化复合微球进行了表征. (4)以带正电荷的PS微球为模板粒子,采用一步法制备了单分散的核-壳型PS/SiO2复合微球和二氧化硅空球.先由St与MTC在乙醇/水的混合介质中发生分散共聚合制备表面带有正电荷的单分散聚苯乙烯微球.由于分散聚合是以乙醇/水为混合溶剂,此介质同时也是二氧化硅前驱体TEOS进行sol-gel反应的St ber溶剂,因此TEOS直接加入到分散聚合完成后的分散液中,氨水催化下TEOS水解,生成的硅羟基因为显负电性而被表面带正电荷的聚苯乙烯微球所捕获,从而在苯乙烯微球表面形成包覆层.同时,虽然乙醇为聚苯乙烯的不良溶剂,但是由于催化剂氨水的加入,碱性的乙醇/水介质能刻蚀PS微球.因此,在二氧化硅壳层形成的同时,PS核被乙醇的氨水溶液刻蚀,从而实现了二氧化硅空心微球的一步法制备,且二氧化硅腔体的厚度(0～100nm)可以通过调节TEOS的浓度来控制.整个制备过程相对简单,而且不需要采用传统无机空心微球制备时所需的溶剂刻蚀,高温煅烧等过程. 关键词:二氧化硅;复合微球;草莓结构;核-壳结构;酸-碱作用;电荷作用;中空微球 Study on the S Preparation and Characterization of Polymer/SiO2 Organic-Inorganic Nanocomposite Spheres Chen Min ABSTRACT In recent years, the strategy to fabricate nano-coating or shell on colloidal particles is of burgeoning interest, principally because such particles can display novel and enhanced properties (e.g. mechanical, chemical, electrical, rheological, magnetic and optical) by independently altering the composition, dimension and structure of the cores and shells. Also the fabrication of such organic-inorganic nanocomposite spheres has received great interest. In this study, polymer/SiO2 organic-inorganic nanocomposite spheres with raspberry-like or core-shell morphology were obtained via surfactant-free methods. Also monodisperse hollow silica spheres based on the PS/ SiO2 nanocomposite spheres were prepared via a one-step method. All the research contents and results are as follows: (1) We firstly used 1-VID as the auxiliary monomer and successfully synthesized a series of long-stand stable raspberrylike PMMA/SiO2 nanocomposite particles via a "soap-free" heterophase polymerization in the presence of an ultrafine aqueous silica sol and water as the continuous phase. Since the surface hydroxyl group of silica particle is acidic, the amino group (basic) of 1-VID should promote the compatibility between polymeric phase and nanosilica phase. Some influencing parameters such as initial silica charge, reaction temperature, 1-VID charge, and pH value on the nanocomposite particles were investigated in detail, and a possible formation mechanism of raspberrylike nanocomposite particles was also discussed. (2) In the second chapter, cationic monomer MTC was used and electrostatic interaction of MTC with aqueous silica particles promote the formation of the nanocomposite particles. Only around 3 % MTC based on monomer mass was copolymerized with MMA in the presence of aqueous silica particles which were simultaneously electrostatically adsorbed onto the surfaces of the organic particles. Since the surface hydroxyl groups of silica particles are hydrophilic, they could act as "Pickering emulsifier" to stabilize the organic particles. The whole process neither required surface treatment for nanosilica particles nor addition of surfactant or stabilizer. It bore out that the electrostatic interaction between negatively charged silica and positively charged MTC was strong enough for the formation of long-stable hybrid microspheres with raspberry-like morphology. (3)In the third chapter, a modified st ber method was proposed to prepare PS/SiO2 hybrid spheres without surface modification or addition of surfactant (stabilizer). Firstly, positively charged PS colloids were prepared via surfactant-free emulsion polymerization of styrene by using azodiisobutyramidinedihydrochloride (AIBA, cationic) as initiator. Hydrolysis and condensation of tetraethoxysilane (TEOS) was carried out in acidic aqueous ethanol medium in the presence of surface positively charged PS colloids. Since silica sols were negatively charged and could be captured rapidly by the positively charged PS colloids, homogeneous nucleation of silica could be avoided and centrifugation/redispersion process of obtained dispersions was unnecessary. By using this method, core-shell PS/SiO2 hybrid spheres with controllable thickness of silica shells could be obtained just by tuning the concentration of TEOS. (4) In the last chapter, we described a novel technique to fabricate PS/SiO2 with core-shell morphology or hollow silica spheres via a one-step process. Firstly, monodisperse positively charged PS particles were prepared via dispersion polymerization of St with 2-(methacryloyl)ethyltrimethylammonium chloride (MTC) in ethanol/water medium. Then hydrolysis and condensation of TEOS was carried out in aqueous ammoniacal alcohol medium at 50℃, in which PS particles were "dissolved" subsequently even synchronously. Neither additional dissolution nor calcination process was needed. Under this condition, all silica formed as the shell on the core particle via the ammonia-catalyzed hydrolysis and condensation of TEOS, no free silica particles were found in the medium. Composite particles with PS as core and silica as shell or hollow silica spheres could be obtained by tinning the concentration of ammonia in the system. Hollow silica spheres with the thickness of 0~100nm could be obtained by adjusting the concentration of TEOS in the formulation. Key words: Silica;Nanocomposite spheres;Raspberry-like;Acid-base interaction;Electrostatic interaction;Core-shell morphology;Hollow spheres |
5楼2009-04-10 09:46:23
6楼2009-04-10 10:10:31