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.

继续本项目的目的是了解玻璃形成分子的动态不对称二元混合物中不同时间和长度尺度上的分子动力学，即动态相当不同的伙伴的混合物，每个组分都有很大差异玻璃化温度。事实证明，在一定的温度范围内，混合物中的大分子已经动态冻结，而较小的成分保留了高度的流动性，后者的动力学表现出所谓的内在限域效应。这些效应包括时间常数与温度相关性的所谓脆到强的转变，特别是对于接近刚性基质的小分子，一种特殊的 A 型玻璃化转变，这是之前通过模式耦合理论预测的某些限制条件下的玻璃化转变。在该项目的后续工作中，对这种内在约束效应进行了研究，并与其他类型的硬约束和软约束的效果进行系统比较。研究将一方面基于项目第一阶段开发的微乳液系统，并提供研究软约束的机会，另一方面也基于我们在多孔 Vycor 基质中过冷二元混合物和液体的光散射经验。因此，可以在不同类型的硬约束和软约束中研究相同的小分子。关于所使用的实验方法，将多散斑相关技术纳入目前的光散射装置中至关重要，以便能够利用偏振和去偏振光子相关光谱有效地研究非遍历和部分遍历系统。通过这种方式，可以通过光散射单独监测分子重新定向以及浓度波动的衰减。特别是，多斑点技术将应用于监测非遍历系统中的分子重新定向。此外，这些测量将与差示扫描量热法、宽带介电谱和准弹性中子散射相结合，以覆盖整个动态范围，并能够消除不同的表面和有限尺寸效应。同时研究了不同时间和长度尺度上浓度波动的衰减，一方面进一步阐明对共混动力学的影响，另一方面了解这些波动的温度依赖性。 X射线光子相关光谱的首次研究表明，混合物上玻璃化转变附近部分冻结浓度波动的干扰行为，其特征是压缩相关函数和所谓的相关时间的弹道波矢量依赖性。这种不寻常的行为将通过多斑动态光散射进行研究。