Poly(ethyl-n-butylsilylene): Structural, thermal, and flow properties of a liquid crystalline polysilane
Poly(ethyl-n-butylsilylene): Structural, thermal, and flow properties of a liquid crystalline polysilane
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聚（乙基正丁基甲硅烷基）：液晶聚硅烷的结构、热和流动特性
DOI：
10.1007/bf00684027
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
R. West
中科院分区：
文献类型：
--
作者：
Tetsuya Asuke;R. West
以乙基-正丁基二氯硅烷为原料，通过钠偶联反应合成了聚乙基-正丁基硅烯（PEBS），并将PEBS分成两个分子量不同的组分，分子量分别为1.4× 106和2.0×104。这两个馏分进行了研究，通过差示扫描量热法和X-射线衍射，紫外光谱，偏光显微镜，和毛细管流变仪，所有作为温度的函数。两种样品在室温及以下均采用六方柱状液晶结构。它们在-20 °C经历弱的吸热转变，低分子量组分在90°C和高分子量组分在170°C时经历一级相变，成为双相液晶形式。低分子量聚合物在106°C下熔化成各向同性液体，高分子量聚合物在185°C下熔化成各向同性液体。两个样品在紫外线下都经历了两个连续的热致变色转变，一个接近一级放热转变，一个接近−20°C转变;讨论了这些热致变色转变的原因。PEBS的流动性能作为分子量的函数进行了研究。
Poly(ethyl-n-butylsilylene) (PEBS) was synthesized by sodium coupling of ethyl-n-butyldichorosilane and separated into fractions with differing molecular weights,Mw=1.4×106and 2.0×104. Both fractions were studied by differential scanning calorimetry and by X-ray diffraction, UV spectroscopy, polarizing optical microscopy, and capillary rheometry, all as a function of temperature. Both samples adopt a hexagonal columnar liquid crystalline structure at room temperature and below. They undergo a weak endothermic transition at −20°C and a first-order phase transition to a nematic liquid crystalline form at 90°C for the low and 170°C for the highMwfraction. Melting to an isotropic liquid takes place at 106°C for the low and 185°C for the highMwpolymer. Both samples undergo two successive thermochromic transitions in the UV, one near the first-order exothermic transition and one near the −20°C transition; the reasons underlying these thermochromic transitions are discussed. Flow properties of PEBS were investigated as a function of molecular weight.