Covalently Cross-Linked Polyelectrolyte Complex Nanoparticles with Enhanced Stability against Dissociation at High Ionic Strength.

Polyelectrolyte complex nanoparticles (PECNPs) often fully dissociate into individual polycations (PC) and polyanions (PA) at high salinities. Herein, we introduce a novel type of colloidally stable PECNP in which the PC is cross-linked, in this case branched polyethylenimine (PEI) to limit this dissociation, even in solutions up to 5.2 M NaCl or 5.

Ultra-stable CO-in-water foam by generating switchable Janus nanoparticles in-situ.

Hypothesis: The surface of silica nanoparticles (NP) may be covalently grafted with two amino ligands to balance colloidal stability and interfacial activity via formation of in situ Janus particles. The modified NP may be combined with a like-charged diamine surfactant to create ultra-stable CO foam at low NP concentrations.

Experiments: The NP colloidal stability was measured up to 80 °C in 230 g/L TDS brine with dynamic light scattering.

Elastic gas/water interface for highly stable foams with modified anionic silica nanoparticles and a like-charged surfactant.

Hypothesis: Surface active anionic nanoparticles (NPs) with strategically designed covalent ligands may be combined with a liked-charged surfactant to form a highly elastic gas-water interface leading to highly stable gas/water foams.

Experiments: The colloidal stability of the NPs was determined by dynamic light scattering, and the surface elastic dilational modulus E' of the interface by sinusoidal oscillation of a pendant droplet at 0.1 Hz, which was superimposed on large-amplitude compression-expansion cycles.