从煤焦油软沥青和苯基硅烷制备硅取代聚芳烃中间相的研究

摘要

过滤后的煤焦油沥青分别与一,二,三,四苯基硅烷在1MPa氩气气氛和420℃～460℃温度下共炭化,合成了硅取代聚芳烃中间相.在四种合成中间相中,元素硅的起始加入量均为2%.测定了裂解残留物和硅的收率、可溶性、玻璃转化温度以及裂解残留物的炭收率;并分别以偏光显微镜和电子探针微分析法考察了残留物的微结构和相应的硅分布,硅的收率取决于不同的苯取代硅烷的挥发性和反应性.裂解残留物显示出三种不同的共存相:(a)含有粗镶嵌织构和痕量硅的光学各向异性相;(b)硅含量较高的光学各向同性相;(c)含细镶嵌织构和中等硅含量的光学各向异性相.最后这种中间相主要来自二,三苯取代硅烷与煤沥青的共炭化,是由于硅取代聚芳烃中碳原子并破坏了其分子的平面结构而引起的.%The synthesis of silicon-substituted polyaromatic mesophase was investigated using a co-pyrolysis of a filtered coal tar soft pitch with mono-, di-, tri-, and tetraphenylsilane. The co-pyrolysis of pitch/silane mixtures containing 2% silicon was studied at a constant argon pressure of 1MPa and temperatures ranging from 420℃ to 460℃. Residue and silicon yields as well as solubility, glass transition temperature and coke yield of the pyrolysis residues were determined. Microstructures of the residues and corresponding silicon distributions were studied by polarized light microscopy and electron probe micro-analysis, respectively. Silicon yields depend on volatility and reactivity of the silanes resulting from the degree of phenyl substitution. The pyrolysis residues show up to three different co-existing phases: (a) an optically anisotropic phase with a coarse mosaic-like texture and negligible silicon content, (b) an optically isotropic phase with high silicon content, and (c) an optically anisotropic phase with a fine mosaic-like texture and medium silicon content. The latter phase, preferentially obtained with di- and triphenylsilane should correspond to a strongly disturbed, silicon-substituted mesophase.