Abstract：
The incorporation of organic groups into sol-gel silica materials is known to have a noticeable impact on the properties and structure of the resulting xerogels due to the combination of the properties inherent to the organic fragments (functionality and flexibility) with the mechanical and structural stability of the inorganic matrix. However, the reduction of the inorganic content in the materials could be detrimental to their thermal stability properties, limiting the range of their potential applications. Therefore, this work aims to evaluate the thermal stability of hybrid inorganic-organic silica xerogels prepared from mixtures of tetraethoxysilane and organochlorinated triethoxysilane precursors. To this end, a series of four materials with a molar percentage of organochlorinated precursor fixed at 10%, but differing in the type of organic group (chloroalkyls varying in the alkyl-chain length and chlorophenyl), has been selected as model case study. The gases and vapors released during the thermal decomposition of the samples under N2 atmosphere have been analyzed and their components determined and quantified using a thermogravimetric analyzer coupled to a Fourier-transform infrared spectrophotometer and to a gas chromatography-mass spectrometry unit. These analyses have allowed to identify up to three different thermal events for the pyrolysis of the organochlorinated xerogel materials and to elucidate the reaction pathways associated with such processes. These mechanisms have been found to be strongly dependent on the specific nature of the organic group.
摘要：
已知有机基团掺入溶胶-凝胶二氧化硅材料对所得干凝胶的性质和结构具有显著影响,这是由于有机片段固有的性质(官能度和柔性)与无机基质的机械和结构稳定性的组合。然而,材料中无机物含量的降低可能对其热稳定性有害，限制了其潜在应用的范围。因此,这项工作旨在评估由四乙氧基硅烷和有机氯三乙氧基硅烷前体的混合物制备的杂化无机-有机二氧化硅干凝胶的热稳定性。为此,一系列四种材料，有机氯前体的摩尔百分比固定在10%，但是有机基团的类型不同（氯烷基在烷基链长度和氯苯基上不同），已被选为示范案例研究。已分析了样品在N2气氛下热分解过程中释放的气体和蒸气，并使用与傅立叶变换红外分光光度计和气相色谱-质谱单元耦合的热重分析仪对其成分进行了测定和定量。这些分析已经允许鉴定用于有机氯干凝胶材料的热解的多达三个不同的热事件,并且阐明与这些过程相关的反应途径。已发现这些机理强烈依赖于有机基团的特定性质。
