Behaviour of polymer-coated composite nanoparticles at bubble-stabilizing interfaces during bubble coarsening and accelerated coalescence: A Cryo-SEM study

Hypothesis

Dynamics of polymer-coated silica composite nanoparticles (CPs) during bubble coarsening is highly dominated by the behaviour of the polymer layer, while in-situ particle aggregation would lead to accelerated bubble coalescence.

Experiments

CPs-stabilized foams were prepared in 0.1 M and 0.55 M Na2SO4 solution, referring to the 0.1 M and 0.55 M foam/bubble respectively. The 0.1 M to 0.55 M transition foam was also prepared. High resolution Cryo-SEM was originally used to investigate the CPs behaviour at the bubble-stabilizing interface during bubble coarsening and accelerated coalescence.

Findings

The 0.1 M bubble-stabilizing interface buckles in uniaxial compression due to coarsening, with the CPs being observed to desorb from the interface. While the CPs were visualized to rearrange into crumpled particle multi-layers surrounding the shrinking 0.55 M bubbles, due to the adhesion between interpenetrating polymer chains and the unique lubrication effect of the PVP layers. The 0.1 M to 0.55 M transition foaming behaviour was also studied. Cracks and voids were observed at interfaces surrounding the transition bubbles driven by in-situ particle aggregation, resulting in accelerated bubble coalescence during the transition process.