Herein, we present an overview of our studies of the morphology, dynamics, and formation of heterogeneous soft matter systems via the emerging technique of liquid phase transmission electron microscopy (LPTEM). This particular subset of materials, more commonly referred to as emulsions, is tremendously commercially and biologically relevant, encompassing applications in food science, commodity materials, and biology. Emulsions operate on the principle of sequestering incompatible phases via a mutually compatible interface, typically an amphiphilic molecule known as a surfactant. It is precisely because of this phase separation that these materials are interesting, but it is also what makes them especially challenging to characterize. Indirect methods (such as scattering) require assumptions about overall material properties, morphology, and population distributions, which are immensely complicated by the multiphasic nature, while conventional imaging techniques have historically required sample fixation to attain the necessary spatial resolution, thereby eliminating the dynamic aspect of these materials. We have shown LPTEM to be an effective way to image these materials in their native, solvated state at unprecedented spatiotemporal resolution. Using this technique, we have examined their morphology, quantified their formation and destabilization, analyzed their motion, utilized them as reaction loci, and observed their stimuli response. We contend that this class of materials is uniquely suited for continued study via this technique not only due to their utility as materials but also because of their tunable contrast, mobility, and stability. Emulsions have the additional benefit of well-defined, modular droplet sizes, which may range from a few nanometers to over a micron. The LPTEM field has consistently encountered issues of spatial confinement which hinder and interfere with in situ reactions and processes. However, if reactants are contained in an emulsion droplet, the degree of confinement is known and controllable. We are confident that further inquiries into such materials will yield insight into more complex processes, such as emulsion polymerization, higher order interface reorganization, and organogel formation. Further, we anticipate that emulsions will be used as in situ microreactors to counteract the artifacts of confinement in LPTEM and control reactions during observation.

Creator

• Vratsanos, Maria A.

DOI

• https://doi.org/10.21985/n2-1vpw-r659

Subject

• Polymer chemistry
• Materials Science

Language

• en

Alternate Identifier

• etdadmin_upload_1009969
• http://dissertations.umi.com/northwestern:16698

Keyword

• liquid phase transmission electron microscopy
• soft matter
• emulsions
• surfactants
• polymers

Date created

• 2023-01-01

Resource type

• Dissertation

Rights statement

• In Copyright