Design and synthesis of surfactants and nanoparticles for mechanistic studies of foams, emulsions and wettability alteration

Surfactants or nanoparticles are shown to stabilize carbon dioxide (CO₂)-in-water (C/W) foams, nitrogen (N₂)-in-water (N/W) foams and CO₂-in-oil (C/O) emulsions and to alter the wettability of oil-wet calcite surfaces to water-wet. Chapter 2 focuses on developing an understanding of the aqueous and interfacial properties of single viscoelastic surfactants to stabilize C/W foams for extended time with highly viscous aqueous phases. Surface modified amphiphilic silica nanoparticles are then investigated as alternatives to surfactants to increase the stability of C/W and N/W foams. Here, the first examples of nanoparticles with known surface modification that stabilize foams in high salinity brines at elevated temperature are presented. The fundamental understanding gained from surfactant design for C/W foam studies is used to design stabilizers for C/O emulsions. Here, polymeric surfactants with polydimethylsiloxane backbones and pendant linear alkyl chains are designed to stabilize novel C/O emulsions despite the low interfacial adsorption driving force, given the low interfacial tension. Finally, silica nanoparticles with various modifications (anionic, cationic and nonionic) are used to mechanistically study wettability alteration of oil-wet calcite surface to water-wet, especially in high salinity environments.