Liquid-cell transmission electron microscopy (LCTEM) is a specialized in situ imaging technique that enables visualization of solvated nanomaterials. Unlike cryogenic (cryo) TEM, LCTEM avoids vitrification and can thus image dynamic and viscous samples and nanomaterials in organic solvents. With LCTEM, researchers have observed solvated polymeric nano-assemblies, the dynamics of such assemblies, and many polymeric biomaterials. However, for such systems, a critical consideration is beam induced solvent radiolysis, which leads to reactive species that can degrade the sample. Given the potential for damage, we worked to understand radiolysis for a prototypical aqueous polymer during LCTEM to ultimately guide future LCTEM studies. We imaged aqueous poly(ethylene glycol) (PEG) with sensitizing gold nanoparticles (GNPs) or scavenging isopropanol (IPA). To quantify damage, we utilized matrix assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS). Our approach confirmed IPA mitigated damage and GNPs enhanced damage. We coupled LCTEM with radiolysis modeling to provide a generalizable strategy for assessing polymer damage. This work highlights the caution required for LCTEM on solvated inorganic particles and the value in exploring scavenging additives to expand the capabilities of LCTEM in polymer science. Additionally, we worked to extend LCTEM to the study of polymeric materials in organic solvents. We defined electron-solvent interactions through Monte-Carlo simulations and radiolysis modeling for two common solvents, N, N-dimethylformamide (DMF) and methanol, and compared these solvents to water. We verified modeled results by studying poly(styrene)-b-poly(4-vinylpyridine) assemblies in the three solvents via LCTEM. MALDI-IMS was then used to verify theoretical results. Our work shows the value of LCTEM in polymer and nano science to characterize materials not amenable to cryo-TEM or other standard techniques.

Studying solvated polymeric nanomaterials with liquid-cell transmission electron microscopy

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.