Soft materials are inherently fluxional, with morphologies and behaviors that are dictated by their solvation state. Thus, many organic systems cannot be reliably imaged by static dry state or cryogenic-transmission electron microscopy (TEM). This motivated us to pursue liquid cell (LC) TEM method development to study our own materials and make the technique generally available. Aiming to expand LCTEM to organic nanomaterials, rather than traditionally studied inorganic systems, the work described in this thesis contributes to a generalizable workflow for studying complex, solution-phase nanomaterials via correlative methods. First, we explored the sensitizing effect of metallic nanoparticles under LCTEM conditions with radiolysis models, LCTEM, and post-mortem matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS). Notably, we showed that metallic nanoparticles can enhance damage to organic components of the system. Soon after, we leveraged variable temperature (VT) LCTEM to uncover the mechanism of thermally triggered fibril formation in diphenylalanine (FF). Here, the superior resolution of LCTEM revealed radial fibril growth for the first time, demonstrating the utility of LCTEM to even well characterized materials. In another thermoresponsive system, we leveraged VT-LCTEM to probe the dynamics of lower critical solution temperature (LCST) block copolymer nanoassemblies. Notably, for a LCST triblock, we leveraged correlative VT small angle X-ray scattering (SAXS) with VT-LCTEM to rigorously characterize a complex morphological transformation, showing the value in leveraging the techniques in tandem. Following these studies on aqueous soft materials, we became interested in probing non-aqueous systems. Specifically, we leveraged modeling, LCTEM, and MALDI-IMS to evaluate the stability of polymeric nanostructures dispersed in different solvents. Ultimately, we observed that non-aqueous, low-density solvents like methanol may be more amenable to LCTEM compared to water. Motivated by this finding, we designed an upper critical solution temperature (UCST) polymer in isopropanol and studied its phase transformations via VT-LCTEM. We turned to liquid resonant soft X-ray scattering (RSoXS) to correlate VT-LCTEM insights. Here, RSoXS shares the same LC holder design used in LCTEM, enabling powerful correlative insight in a fixed sample geometry. Ultimately, these developments continue to push the LCTEM field towards becoming a reliable and robust method for studying solution-phase processes in nanomaterials of all kinds.

Creator

• Korpanty, Joanna

DOI

• https://doi.org/10.21985/n2-vsb7-d059

Subject

• Chemistry

Language

• en

Alternate Identifier

• http://dissertations.umi.com/northwestern:16391
• etdadmin_upload_954956

Date created

• 2022-01-01

Resource type

• Dissertation

Rights statement

• In Copyright