Interfacial Properties of Polymeric Nanomaterials
Doctor of Philosophy
Polymeric nanomaterials such as nanoparticles and branched polymers are interfacially active and can be used to stabilize or increase the viscosity of an emulsion, which is potentially useful for enhanced oil recovery (EOR) process. However, nanoparticles can be limited in terms of compatibility with different environments, such as elevated salinities and temperature and present challenges for demulsification. The research presented in this dissertation mainly focuses on my work on the development of polymer-coated nanoparticles (PNPs) which are amphiphilic, surface active, and stimuli-responsive. Polymer-coated nanoparticles are prepared by covalently grafting polymers to the surface of the nanoparticles. The interaction of the PNPs with the environment can be tailored through variation of the polymer attached to the nanoparticle surface. In Chapter 2 is the work on the development of carbon black which can segregate to oil-water-surfactant bicontinuous microemulsions. These PNPs are prepared by attaching hydrophobic and hydrophilic chains to the surface of carbon black nanoparticles. By tuning the surface charge through variation of the degree of sulfation, the hydrophobic/hydrophilic properties and stability can be tuned. We find that highly-sulfated PNPs are stable to elevated salinities and spontaneously segregate to oil-water-surfactant microemulsions. Chapter 3 is the development of pH-responsive PNPs. These are prepared by grafting a pH-responsive polymer to silica nanoparticles. These nanoparticles can emulsify crude oil, and be quickly demulsified through a change in pH. We demonstrate that the use of 0.1 wt % of pH-responsive PNPs enhance the recovery of crude oil in a sandpack. This work demonstrates the versatility and potential of PNPs for a variety of applications, including oil recovery, controlled emulsification and demulsification, and reduction of interfacial tension. Chapter 4 is the study of aqueous self-assembly of bottlebrush block copolymers, which have similarity to polymer-coated nanoparticles in many aspects. It is able to self-assemble rapidly to form structures with large periodic domains and form stable micelles with very low critical-micelle concentrations (CMC). In this work, we have studied a library of amphiphilic bottlebrush polymers with different ratio of hydrophilic and hydrophobic chains, and demonstrated a lower CMC of bottlebrush polymer over linear copolymers. Some primary work to quantify the self-assembly of a model library of amphipilic bottlebrush block polymers through small-angle neutron scattering (SANS) measurement is discussed.
emulsion; nanoparticle; bottlebrush polymer; EOR