Dynamic Light Scattering in Binary Glass Forming Systems -- Concentration Fluctuations, Secondary Processes and Relaxation in Confinement

二元玻璃成型系统中的动态光散射——浓度波动、二次过程和约束松弛

基本信息

批准号：
19677864
负责人：
Professor Dr. Thomas Blochowicz
金额：
--
依托单位：
Institut für Physik Kondensierter Materie (IPKM)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2006
资助国家：
德国
起止时间：
2005-12-31 至 2016-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/19677864?language=en
关键词：
Dynamic Light Scattering Binary Glass

项目摘要

The aim of the continuation of the present project is to gain an understanding of the molecular dynamics on different time- and lengthscales in dynamically asymmetric binary mixtures of glass forming molecules, i.e., mixtures of dynamically rather different partners, with a large difference in each components Tg. It turns out that within a certain temperature range, where the large molecules in such a mixture a already dynamically frozen, the smaller component retains a high degree of mobility, and the dynamics of the latter shows so-called intrinsic confinement effects. These effects include a so-called fragile-to-strong transition in the temperature dependence of the time constants and in particular for small molecules close to the rigid matrix a peculiar Type-A glass transition, which was previously predicted by mode-coupling theory for the glass transition in certain confinement situations. In the continuation of the project such intrinsic confinement effects are investigated and systematically compared to effects of other kinds of hard and soft confinement. The investigations will be based on the one hand on the microemulsion systems, which were developed in the first period of the project and provide the opportunity to study soft confinement and also on our experience of light scattering of supercooled binary mixtures and liquids in porous Vycor matrices. Therefore it will be possible to study the same small molecule in different types of hard and soft confinement. Concerning the experimental methods used, it will be crucial to include the multi-speckle correlation technique into the present light scattering setup, in order to be able to efficiently study non-ergodic and partially ergodic systems with polarized and depolarized photon correlation spectroscopy. In this way molecular reorientation as well as the decay of concentration fluctuations can be separately monitored by light scattering. In particular, the multispeckle-technique will be applied to monitor molecular reorientation in non-ergodic systems. In addition, these measurements will be combined with differential scanning calorimetry, broadband dielectric spectroscopy and quasielastic neutron scattering to cover the full dynamic range and be able to disentangle different surface and finite-size effects. At the same time the decay of concentration fluctuations is investigated at different time- and lengthscales, on the one hand to further clarify the influence on the blend dynamics and on the other hand to understand the temperature dependence of these fluctuations. First studies with X-ray photon correlation spectroscopy indicate jamming behavior of partially frozen concentration fluctuations in the vicinity of the mixtures upper glass transition, which is characterized by compressed correlation functions and a so-called ballistic wave-vector dependence of the correlation times. This unusual behavior will be investigated by multispeckle dynamic light scattering.

本项目延续的目的是了解动态不对称二进制二进制组合分子的分子动力学的理解，即形成分子的玻璃分子，即动态较为不同的伴侣的混合物，每个组件TG的混合物都有很大的差异。事实证明，在一定温度范围内，这种混合物中的大分子已经动态冷冻，较小的组分保留了高度的迁移率，而后者的动力学表现出所谓的内在限制效应。这些效果包括在时间常数的温度依赖性中，尤其是接近刚性矩阵的小分子的所谓脆弱到突变的跃迁，它特有的A型玻璃转变，以前是在某些限制情况下通过玻璃过渡的模式偶联理论预测的。在该项目的延续中，研究并系统地研究了这种内在的限制效应，并将其与其他类型的硬限制和软限制的影响进行比较。该研究将基于对微乳液系统的一方面，该系统是在项目的第一阶段开发的，并提供了研究软限制的机会，也提供了我们在多孔Vycor矩阵中超冷的二元混合物和液体光散射的经验。因此，可以在不同类型的硬和软限制中研究相同的小分子。关于所使用的实验方法，将多销子相关技术包括在当前的光散射设置中至关重要，以便能够有效地研究具有极化和去极化光子相关光谱的非凝治和部分偏高的系统。这样，可以通过光散射分别监测分子重新定位以及浓度波动的衰减。特别是，将应用多销售技术来监测非共基系统中的分子重新定位。此外，这些测量结果将与差分扫描量热法，宽带介电光谱和准中子中子散射结合使用，以覆盖完整的动态范围，并能够解散不同的表面和有限尺寸的效果。同时，一方面研究了浓度波动的衰减，以进一步阐明对混合动力学的影响，另一方面，以了解这些波动的温度依赖性。 X射线光子相关光谱的第一研究表明，混合玻璃上玻璃转变附近部分冷冻浓度波动的障碍行为，其特征是压缩相关函数和相关时间的所谓弹道波矢量依赖性。这种异常的行为将通过多销钉动态光散射来研究。