过冷液态醇的德拜型介电弛豫及其热力学关联

项目名称： 过冷液态醇的德拜型介电弛豫及其热力学关联

项目编号： No.10804093

项目类型： 青年科学基金项目

立项/批准年度： 2009

项目学科： 轻工业、手工业

项目作者： 王利民

作者单位： 燕山大学

项目金额： 24万元

中文摘要： 本项目根据申请书研究内容与研究目标对单羟基醇的德拜型介电弛豫以及其热力学上的关联进行了研究。通过使用宽频介电谱对同质异构的单羟基醇与多羟基醇在过冷液区内进行了测量，建立了德拜弛豫与结构弛豫动力学与分子结构的关系。也发现了一系列德拜弛豫新的动力学特征，包括德拜弛豫的宽化能力与弛豫强度在混合条件下的过剩行为。在热力学的研究方面，我们建立了通过焓弛豫研究单羟基醇在玻璃化转变中的热行为，并建立了液体强弱性参数与弛豫焓之间的关联。通过对单羟基醇的退火研究发现，德拜弛豫动力学尽管不直接地决定玻璃转变的发生，但也有可能对玻璃转变热力学有一定贡献。根据这些单羟基醇的动力学与热力学方面的研究结果，我们一方面对已有的德拜型弛豫模型进行了检验，例如，最近流行的单羟基醇液体中的瞬态链模型，发现这一模型并不能解释这些新的德拜弛豫动力学。尽管对于德拜型介电弛豫的物理起源仍在探讨之中，我们提出基于电偶极矩的分子（或者分子链）转动极化不能有效地解释这些德拜动力学特征，而空间电荷极化最有可能解释这些实验结果。相关结果发表了16篇学术论文，其中SCI文章15篇，包括APL、PRB、JPCB、JCP等期刊。

中文关键词： 玻璃转变；过冷液体；介电弛豫；焓弛豫；单羟基醇

英文摘要： The studies of the project proceed in terms of the Outlines and Objectives described in the proposal aiming at understanding the extra Debye relaxation in monohydroxy alcohols and its thermodynamic correlation. The application of broad frequency dielectric spectrometer allows characterizing some new dynamic features of monohydroxy alcohols that concern largely the broadening behavior of relaxation dispersion and the mixing effect on the relaxation strength. We found that broadening of relaxation dispersion of Debye relaxation occurs when the molecular size of the monohydroxy alcohols is large enough. Of more interest is that the broadening gets even worse with temperature, which is totally different from what has been observed in structural relaxation. When mixed with other monohydroxy alcohols, the Debye relaxation strength might be subject to an anomalous increase. The thermodynamic studies focuses on the enthalpy relaxation determination of relaxation heat involved in glass transition and liquid fragility of the monohydroxy alcohols together with other generic liquids, and the relaxation heat/enthalpy is found to correlate with liquid fragility. The annealing studies of glasses show that the Debye relaxation might do some contribution to the glass transition thermodynamics, albeit it does not directly determine the glass transition. The dynamic and thermodynamic studies allow us to check previous models, for example, the transient chain model, in interpreting the physics of the Debye relaxation. We found that the models fail to explain the experimental observation as long as the rotation polarization mode is still thought as a consequence of the presence of high dipole moment of a chain or a cluster. We propose that the Debye relaxation might be generated from space charge polarization. 16 papers have been published with the experimental results covering the journals of APL, PRB, PRE, JCP and JPCB. The kind support of the NSF funding is greatly appreciated.

英文关键词： glass transition; supercooled liquids; dielectric relaxation; enthalpy relaxation; monohydroxy alcohols