中間相高分子聚二乙基矽氧烷及聚二甲基矽氧烷流變行為研究

Rheological Study of Mesophase Polydiethylsiloxane and Polydimethysiloxane

劉家樺(Chia -Hua Liu)

指導教授 ： 芮祥鵬

國立臺北科技大學/工程學院/有機高分子研究所/碩士(2010年)

摘要

聚二乙基矽氧烷poly(diethylsiloxane)為柱狀中間相的柔軟主鏈型熱向性高分子，其中間相的溫度範圍是根據其分子量的大小，其結晶狀態主要為α相及β相及γ相，三種形態，結晶型態上有趨向動力學穩定之單斜堆積α相，及熱力學上較為穩定的四方堆積β相，及結晶形態類似β相之γ相。在此次研究上，利用流變儀觀察聚二乙基矽氧烷在中間相時之流變行為，及動態黏彈性測試，並將其與分子量相近之聚二甲基矽氧烷poly(dimethylsiloxane)作比較，發現聚二乙基矽氧烷在中間相時因其轉變為黏塑體，黏度提高；動態黏彈性測試中，於中間相溫度時黏性與彈性皆提升，相較於聚二甲基矽氧烷，在相同受測溫度範圍內，其為一般高分子行為之剪稀現象，並且其彈性及黏性並無太大變化。
另外，由DSC熱分析、POM偏光顯微觀察、流變儀分析可得到聚二乙基矽氧烷的中間相溫度範圍約在7℃至17℃之間，並且其中間相溫度內之黏度及動態模數皆提升，是因其發生假性交聯行為，由動態模數在中間相溫度區間內隨剪切應變率升高而逐漸下降的現象，得知其原因為假性交聯結構鬆開之故。在聚二甲基矽氧烷及非中間相溫度區間之聚二乙基矽氧烷並無此現象發生。

關鍵字

中間相高分子 ； 假性交聯 ； 黏塑體

並列摘要

poly(diethylsiloxane) (PDES) is a flexible main-chain isotropic polymer which has columnar mesophase depending on molecular weight. High molecular weight PDES has been shown to crystallize into two different modifications: α and β phase PDES. Preferably kinetic α phase is a monoclinic packing and the thermodynamically more stable β phase has formed tetragonal lattice. A third crystalline modification has been reported for low molecular weight PDES. This modification, designated γ PDES, was found to closely resemble the tetragonal β modification. This study is employed by a parallel plate rheometer to compare the viscosities of mesophase PDES and PDMS under the changes in temperature. An apparent increase in viscosity and dynamic viscoelastic properties were found when PDES was in the isotropic temperature range. It was attributed to the formation of viscoplastic body caused by pseudo crosslinking. In contrast, PDMS demonstrates common shear thinning behavior and its viscoelastic properties are unchanged.
Moreover, PDES is performed by differential scanning calorimetry (DSC) and polarizing optical microscope (POM) and parallel plate rheometer (Physica MCR 301) to conform that mesophase temperature range is between 7℃and 17℃. The viscosity and dynamic viscoelastic properties decreased with the climbing percentage of shear strain due to the loosening of pesudo crosslinking networks. The phenomena of amorphous PDES and PDMS do not occur.

並列關鍵字

mesopahse polymer ； pseudo crosslinking ； viscoplastic

參考文獻

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