Dielectric relaxations in thermotropic liquid crystalline polypeptides

IEEE Transactions on Electrical Insulation Pub Date : 1993-02-01 DOI:10.1109/14.192248

E. Neagu, R. Neagu, W. Daly, I. Negulescu

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引用次数: 8

Abstract

Thermally stimulated depolarization current (TSDC) and thermally stimulated polarization current (TSPC) measurements and the differential scanning calorimetry (DSC) method have been used for the investigation of thermal transitions in thermotropic poly( gamma -stearyl- alpha , L-glutamate). The beta peak (-80 degrees C) and alpha /sub 1/ and alpha '/sub 1/ peaks registered between -50 degrees C and 25 degrees C were attributed to movements of side chain dipoles. The alpha /sub 2/ peak, observed approximately=43 degrees C, was indicative of the melting of paraffinic side chains. The activation energies were determined for beta peaks and alpha /sub 2/ peaks at different heating rates. A good correlation between heating rate and the square of the maximum peak temperature was found, showing that these peaks are of dipolar origin. The alpha /sub 1/ and alpha /sub 2/ peaks were strongly influenced by thermal treatments. The position of alpha /sub 2/ was close to that determined by DSC. Depending on the thermal history of samples, the paraffinic side chain segments melted and crystallized over a large temperature range, suggesting the formation of crystallites with different dimensions. >

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热致液晶多肽中的介电弛豫

采用热激去极化电流(TSDC)和热激极化电流(TSPC)测量和差示扫描量热法(DSC)研究了热致性聚(γ -硬脂酰- α， l-谷氨酸)的热转变。β峰(-80°C)和α /sub 1/和α '/sub 1/峰记录在-50°C和25°C之间归因于侧链偶极子的运动。在约=43℃时观察到的α /亚2/峰表示石蜡侧链的熔化。测定了不同升温速率下β峰和α /sub 2/峰的活化能。升温速率与最高峰温度的平方之间有很好的相关性，表明这些峰是偶极起源的。α /sub 1/和α /sub 2/峰受热处理的影响较大。α /sub 2/的位置与DSC测定的位置接近。根据样品的热历史，石蜡侧链段在很大的温度范围内熔化和结晶，表明形成了不同尺寸的晶体。>

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IEEE Transactions on Electrical Insulation

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