Synthesis of Amphiphilic Materials for the Investigation of Dispersant Dynamics and Nanoparticle End-Group Presentation

Abstract

Amphiphiles – compounds that possess both hydrophilic and hydrophobic properties – are ubiquitous in nature and the chemical industry. Due to their dual character, amphiphilic compounds tend to be surface active and self-aggregate in solution, leading to applications as emulsion stabilizers, scaffolds for complex materials, and containers for drug delivery. Due to their wide use, surfactants are a large industry, estimated at $30 billion in 2016. The overall theme of this thesis is the synthesis and design of amphiphiles for applications in oil spill remediation and nanomedicine, and is divided into two parts.

Part 1 (Chapters 2 and 3) focuses on the challenges of dispersant use motivated by the 2010 Deepwater Horizon oil spill. Since Deepwater Horizon was the first instance of a deep sea spill, dispersant packages or remediation protocols had not yet been developed to handle the blowout, leading to the release of ~50 million liters of oil. Dispersant treatment at the wellhead demonstrated a new approach to remediating a deep sea spill, but also illuminated the need to better understand dispersant dynamics and to formulate dispersants that better stabilize oil droplets that rise through the ocean. Chapter 2 introduces a novel approach to visualize dispersants using surfactant-dyes to study structure-property relationships of surfactants. Chapter 3 discusses the effects of polymer-surfactant mixtures – for potential long time oil droplet stability – on short time dispersant adsorption by dynamic interfacial tension measurements.

Part 2 (Chapter 4) covers the challenge that hydrophobic end-groups can cause in the decoration of polymeric nanoparticles (NPs) for drug delivery applications. Our work applies techniques developed to visualize dispersants to the investigation of poly(ethylene glycol) end-groups on polymeric NPs. We also discuss preliminary findings in NP-ligand conjugation studies that investigate the effects of end-group hydrophobicity and ligand size on conjugation yield.

In summary, the research presented in this thesis has resulted in methods to determine tethered end-groups’ environment on NPs, visualize surfactants, and investigate dynamic surface tensions of polymer-surfactant solutions with implications in oil spill remediation and drug delivery. The synthetic and experimental methods developed here provide a platform from which further fundamental and applied work can be conducted.