【作者】 靳海英；

【导师】 车顺爱；

【作者基本信息】 上海交通大学 ， 应用化学， 2009， 博士

【摘要】 高度有序的手性介孔二氧化硅是最近发现的一种新型介孔材料,受到化学、材料学等多学科的普遍关注。这是由于它不仅具有介孔材料高有序度、高比表面积、大孔容、孔径可调的优点,而且还拥有独特的手性孔道结构。它在手性吸附分离、手性纳米材料的合成以及手性催化等方面具有巨大的应用潜力。但是,这个新兴领域还存在很多问题有待于我们去解决。本论文将围绕如何控制手性介孔二氧化硅的合成,影响手性形貌形成的各种因素,以及解释手性形貌形成机理等方面进行了详细研究。本文包括以下几部分内容:第一章,前一部分综述了手性材料的基本特性及有机手性材料中的手性超分子聚集体和手性液晶;后一部分综述了无机手性材料的制备方法和手性介孔材料的发展现状。第二章,通过改变合成过程中搅拌速度合成了各种不同结构的二氧硅介孔材料以及有效地控制了其形貌。本文以手性阴离子表面活性剂十四烷基丙胺酸钠(C14-L-AlaS)为模板,以3-胺丙基三乙氧基硅烷(APES)为助结构导向剂,以正硅酸乙酯(TEOS)为无机硅源合成了介观结构高度有序的手性介孔材料。当搅拌速度低于300 rpm时,形成了不同结构、不同螺距、不同半径、不同长短的手性介孔材料以及不同的螺旋飘带介孔材料。搅拌速度升高到400-800 rpm时,手性介孔材料的形貌变得均一,而且其半径随着搅拌速度的增加而增加,而长度变短。手性介孔材料的螺距随着粒子直径的增加而增加,而二者比值保持一定值不变。XRD、SEM和TEM表征结果表明不同搅拌速度下所得到的不同形貌的手性介孔材料均具有高度有序的二维六方p6mm结构。不同搅拌速度下得到的手性介孔材料中左手方向所占的比例均为75%,不随搅拌速度的改变而改变。第三章,通过改变合成温度首次合成出纯左或右手方向螺旋飘带状介孔材料,并考察了其形成过程。C14-L-AlaS-APES-TEOS的合成体系,在0、10、15和20 oC反应温度下分别形成具有螺旋飘带、空心球、飞碟和手性四种形貌的二氧化硅介孔材料。研究发现:(1)具有螺旋飘带形貌介孔材料的墙壁由两套无序的孔道组成;空心球形貌介孔孔道指向球心排列;而飞碟和手性介孔材料孔道为高度有序的二维六方结构;(2)这四种形貌二氧化硅介孔材料均从表面活性剂的具有层状结构的直带形貌转变而来,而其中螺旋形貌的二氧化硅是通过固-固转变形成,空心球、飞碟和手性棒状二氧化硅材料是通过直带溶解之后转变而形成;(3)具有螺旋飘带形貌二氧化硅介孔材料是纯右手的,而手性棒状形貌二氧化硅介孔材料(CMS)中左手所占的比例是75%;(4)螺旋飘带形貌介孔材料只有由手性表面活性剂为模板才能形成,而手性介孔材料由手性、非手性和外消旋的表面活性剂为模板均可形成。第四章,通过设计合成手性介孔材料的方法,找出了优化合成条件。针对手性阴离子表面活性剂(Cn-L-AlaS)为模板,N-三甲氧基丙基硅烷-N,N,N-三甲基氯化铵(TMAPS)为助结构导向剂的手性介孔材料的合成体系研究了反应体系中表面活性剂的离子化程度、助结构导向剂与表面活性剂的摩尔比、反应温度、表面活性剂的碳链长度以及反应使用的碱的种类等反应条件对合成手性介孔材料介观结构,孔径和形貌的影响。研究发现:(i)手性介孔材料的介观结构存在于二维六方相的一狭小范围内,二维六方结构与层状相和Ia3d相相邻;(ii)手性介孔材料在很小范围表面活性剂胶束曲率下形成,胶束曲率可以通过调节表面活性剂的离子化程度、助结构导向剂与表面活性剂的摩尔比以及表面活性剂的碳链长度来调节;(iii)手性介孔材料在反应温度为25-100 oC范围内都能形成;(iv)反应体系中碱的种类能影响手性介孔材料的孔道直径的大小,却不能影响手性介孔材料的方向性。更多还原

【Abstract】 The highly ordered chiral mesoporous silica have attracted much interest in the chemistry and material communities because of their helical pore structure, high surface areas, large pore volume and tailorable pore size. It is thought to have great application potentiality in selective adsorption and separation, synthesis of chiral nano materials, and asymmetric catalysis. However, there are still a lot of problems to solve in this new field. In this thesis,the synthesis of the chiral mesoporous silica, the mechanism of such synthesis and the factors of chiral mesoporous silica will be discussed. There are four parts in this thesis:In chapter 1, the basic character of chiral materials and organinc chiral material including chiral supramolecular assembling and chiral liquid crystal were firstly reviewed. Then, the synthesis mechanism of inorganic materials and the current studies on the chiral mesoporous materials were reviewed.In chapter 2, chiral ordered mesoporous silica was synthesized by using chiral surfactant N-myristoyl-L-alanine sodium salt (C14-L-AlaS) as template, 3-aminopropyltriethoxysilane (APES) as co-structure directing agent (CSDA) and tetraethoxylsilane (TEOS) as inorganic source. The morphology and chiral structure clearly depend on the stirring rate. When the stirring rate is lower than 300 rpm the samples show diverse morphologies: twisted ribbon like and various twisted rod like structures with different chiral pitches. The morphologies become uniformly twisted rod with a hexagonal cross-section when the stirring rate is increased to 400 rpm, 600 rpm and 800 rpm. The samples synthesized at rate faster than 1200 rpm showed non-helical morphology. The outer diameter of rod was increased with increasing stirring rate and the pitch length was also increased with increasing of the rod diameter with constant pitch/rod diameter ratio of ~15.5. It can be considered that the same 2d-hexagonal p6mm structure with the same pore size and wall thickness has been formed regardless of the stirring rate. The left-/right-handedness ratio is proved to be ca. 7.5/2.5 for the total samples regardless of the difference in stirring rate or direction as far as the rate is faster than 400 rpm.In chapter 3, using lipids (N-acyl amino acid) and APES as structure and costructure directing agents, mesoporous silicas with four different morphologies, that is helical ribbon (HR), hollow sphere, circular disc and helical hexagonal rod were synthesized only by changing synthesis temperature from 0 to 10, 15 and to 20°C. Their structures were studied by electron microscopy. It has been found that (i) they have structures double-layer disordered mesopores in HR and radially oriented mesopores in the hollow sphere, and highly ordered straight and chiral 2d-hexagonal mesopores in the disk-like and helical rod, respectively; (ii) these four types mesoporous silicas were transformed from the flat bilayered lipid ribbon with the chain-interdigitated layer phase through solid-solid transformation for HR formation and dissolving procedure transformation for hollow sphere, circular disc and twisted morphologies, respectively; (iii) the mesoporous silica helical ribbon was exclusively right-handed and the 2d-hexagonal chiral mesoporous silica was left-handed excess when L form N-acyl aminoacid has been used as lipid template; (iv) the HR has been formed only by the chiral lipid molecules and the 2d-hexagonal chiral mesoporous silicas have been formed chiral, achiral and racemic lipids.In chapter 4, chiral mesoporous silica with highly ordered helical nano-sized channels was synthesized by using chiral anionic amphiphilic molecules (N-acyl-L-alanine) as template upon a CSDA method. Synthetic conditions, such as ionization degree of the surfactant, CSDA/surfactant molar ratio, reaction temperature, the carbon chain length, and the type of counterions have been extensively studied. It was found that: (i) in the synthesis-space diagram of mesophases, the CMS mesostrucrue locates within the area of two dimensional (2D-) hexagonal which is a neighbor of lamellar and bicontinuous Ia3d mesostructures; (ii) the generation of CMS demands very rigorous micellar curvature which was mainly controlled by the ionization degree of the surfactant controlled by acid addition amount, CSDA/surfactant molar ratio and the carbon chain length; (iii) the CMS can be synthesized in a wide reaction temperature range of 25-100 oC; and (iv) the pore diameter of the CMS was decreased with decreasing size of the counterion.更多还原