由离子液体辅助的四乙氧基硅烷快速凝胶化得到的低密度离子凝胶。
Low density ionogels obtained by rapid gellification of tetraethyl orthosilane assisted by ionic liquids.
机构信息
Ionic Liquid and Solid State Ionics Laboratory, Department of Physics, Banaras Hindu University, Varanasi- 221005, India.
出版信息
Dalton Trans. 2012 May 28;41(20):6263-71. doi: 10.1039/c2dt30318c. Epub 2012 Apr 3.
A non-hydrolytic one pot sol-gel method has been used to synthesize mesoporous silica ionogels with the confined ionic liquid (IL) 1-ethyl 3-methyl imidazolium tetra fluoro-borate [EMIM][BF(4)]. The precursor for obtaining the SiO(2) matrix was tetraethyl orthosilicate (TEOS) and formic acid was used as a catalyst. These ionogels have been characterized by density measurements, TEM, BET, DSC, TGA and FTIR. The incorporation of the ionic liquid [EMIM][BF(4)] enhances the gellification rate which results in the ionogels having very low density (0.3 g cm(-3)). The low density has been explained on the basis of the creation of 'blind embedded pores' in the matrix (apart from open pores) due to very rapid gellification (1 min). Morphological studies provide experimental evidence for the presence of blind pores/voids inside the ionogel ingots. We have also shown that the IL entrapped in nanopores (~7-8 nm pore size) of the SiO(2) matrix has different physical properties than the bulk IL viz. (a) the phase transition temperatures (T(g), T(c) and T(m)) of the IL change upon confinement, (b) the thermal stability reduces upon confinement, and (c) the pore wall interaction with the IL results in changes in the C-H vibrations of the imidazolium ring and alkyl chain (the former increasing) which is also indicated in our DFT-calculation.
已采用非水解一锅溶胶-凝胶法合成了具有受限离子液体(IL)1-乙基-3-甲基咪唑四氟硼酸盐[EMIM][BF4]的介孔硅质离子凝胶。获得 SiO2 基质的前体是正硅酸乙酯(TEOS),甲酸用作催化剂。这些离子凝胶通过密度测量、TEM、BET、DSC、TGA 和 FTIR 进行了表征。离子液体[EMIM][BF4]的掺入增强了胶凝速率,从而使离子凝胶具有非常低的密度(约 0.3 g cm-3)。这种低密度是基于基质中形成“盲埋孔”(除了开孔之外)来解释的,这是由于胶凝非常迅速(约 1 分钟)。形态研究为离子凝胶锭内部存在盲孔/空隙提供了实验证据。我们还表明,纳米孔(~7-8nm 孔径)中的 SiO2 基质中捕获的 IL 具有与体 IL 不同的物理性质,即(a)IL 的相转变温度(Tg、Tc 和 Tm)在受限时发生变化,(b)热稳定性在受限时降低,以及(c)孔壁与 IL 的相互作用导致咪唑环和烷基链的 C-H 振动发生变化(前者增加),这在我们的 DFT 计算中也得到了表明。