Intermolecular Structure and Dynamics in Multicomponent Glasses

聚合物玻璃是许多坚固、轻质材料的基础。这些材料的工程性能和加工特性可以通过添加低分子化合物、第二聚合物组分或增强颗粒或纤维来改变和控制。组分之间的相互作用在决定所得材料的均匀性、玻璃化转变和模数等特征方面起着关键作用。基于碳-13自旋扩散的核磁共振新技术可以在聚合物重复单元的化学基团水平上探测组成成分的相对分子结构。通过这一级别的结构数据，可以识别导致相容或弹性系数增加等性能的化学相互作用。模数的变化通常反映玻璃中存在的局部链动态，而核磁共振是识别这些特征的一个特别强大的工具。稀释剂、二次聚合物或填充剂对局部动力学的影响可以增强单元级结构。要研究的材料包括两种具有强相互作用的聚合物共混物，其中兼容性不受氢键控制，并且核磁共振是确定相互作用性质的首选技术。还将研究一类特殊的低分子稀释剂，它们是特别有效的抗塑化剂。此外，还将从核磁共振波谱的局部结构特征出发，研究工程树脂在增强纤维存在下的相互作用和迁移率的变化。

Polymeric glasses serve as the basis for many strong, lightweight materials. The engineering properties of these materials and the processing characteristics can be modified and controlled by addtion of low-molecular-weight compounds, a second polymeric component, or a reinforcing particle or fiber. The interactions between the components play a critical role in determining features such as homogeneity of the resultant material, the glass transition and the modulus. A new nuclear magnetic resonance technique based on carbon-13 spin diffusion can probe the relative intermolecular structure of the constituent components at the level of the chemical groups of the polymer repeat unit. With this level of structural data, the chemical interactions leading to properties such as compatibility or increase in modulus can be identified. Changes in the modulus typically reflect the local chain dynamics present in the glass and NMR is a particularly powerful tool for identifying these features. The influence of diluents, a second polymer or a filler on the local dynamics can reinforce the unit level structure. The materials to be studied include two polymer blends with strong interactions where compatibility is not controlled by hydrogen bonding and where NMR is the technique of choice for identifying the nature of the interaction. A special class of low molecular weight diluents which are particularly effective antiplasticizers will also be investigated. In addition, the interactions and changes in mobility of an engineering resin in the presence of a reinforcing fiber will be studied from the local structural viewpoint characteristic of NMR spectroscopy.