Probing diffusion and molecular dynamics to study self-assembly and intermolecular interactions in macromolecular and colloidal systems using NMR diffusometry and spectroscopy

Abstract

The growing demand for technological advancements in energy storage and pharmaceuticals, driven by population growth and climate change, has created an urgent need for the development of novel materials with finely tuned and targeted properties. Polymers, with their inherent versatility, have emerged as key players in modulating the functionality of such advanced materials. However, achieving precise control over the performance of the materials requires a deep understanding of the molecular interactions, self-assembly processes, and transport phenomena that govern their behavior at the nanoscale. This dissertation focuses on the application of advanced nuclear magnetic resonance (NMR) techniques to probe the molecular dynamics and diffusion behavior in complex macromolecular and colloidal systems. Two key NMR techniques – NMR diffusometry and dynamic NMR spectroscopy – are employed to probe the motion and exchange process of molecules within these systems. By providing insights into the dynamics of the constituents, these methods are particularly powerful in unraveling the intermolecular interactions that govern material functionality. The materials under investigation include block copolymer micelles (BCMs), ligand-capped quantum dots (QDs), and linear polyelectrolyte chains – each with unique structural characteristics and promising applications. Block copolymer micelles are of particular interest for drug delivery applications due to their ability to encapsulate and release therapeutic agents in controlled manner. Colloidal quantum dots, with their size-tunable electronic properties, have great potential in photovoltaics and biosensing. Linear polyelectrolytes, characterized by their charged backbones, are crucial for energy storage and biomedical applications. Through a detailed analysis of the translational motion of molecules, this work reveals key molecular insights, including intermolecular interactions, the coexistence of molecules in distinct chemical environments, and their exchange mechanism between these environments. These findings establish critical structure-property relationships in each material system, providing a foundation for rational design and optimization of their functional performance. The results obtained in this research not only contribute to our fundamental understanding of the molecular behavior of these complex systems but also have practical implications for design of next-generation materials. By leveraging the power of NMR-based techniques, this dissertation offers a pathway for enhancing material properties in the desired applications. The findings emphasize the critical role of molecular characterization techniques in advancing the field of material science and facilitating the development of more efficient, high-performance materials tailored to meet the demands for modern technology.