The interaction between two millimeter-sized air bubbles in n-dodecane was analyzed using a high-speed video camera. The two bubbles were grown in the presence of either poly(lauryl methacrylate)-poly(benzyl methacrylate) [PLMA29-PBzMAx] spherical nanoparticles (where x = 50, 249, or 496) or PLMA18-PBzMA55 worms. The effect of varying the spherical nanoparticle diameter was investigated by comparing the behavior of bubbles stabilized by 22 nm, 60 nm or 100 nm spheres. In each case, dynamic surface tensiometry studies confirmed that these nanoparticles lowered the n-dodecane/air interfacial tension, with the largest nanoparticles providing the greatest reduction. This provides evidence for nanoparticle adsorption at this interface. For short aging times (&lt; 2 minutes) the bubble coalescence behavior was independent of the nanoparticle diameter, but longer aging times (&gt; 5 minutes) led to more effective bubble stabilization by the largest spherical nanoparticles. The influence of copolymer morphology on air bubble stability was investigated by exploiting the thermoresponsive behavior of the PLMA18-PBzMA55 worms. When heated to 150 °C, these worms undergo a worm-to-sphere transition, which is essentially irreversible when performed at low copolymer concentration (&lt;1 % w/w). This morphological transition enabled the direct comparison of spheres or worms prepared from a single diblock copolymer, which should minimize any difference in surface wettability. Interfacial tension data suggested that PLMA18-PBzMA55 spheres of 36 nm diameter reduced the surface tension of the air/n-dodecane interface more than the corresponding PLMA18-PBzMA55 worms. Similarly, using spherical nanoparticles led to longer coalescence times than the worms, indicating that the former are more effective stabilizers of millimetre-sized air bubbles in n-dodecane.

Giant non-aqueous Pickering bubbles: Effect of nanoparticle diameter and morphology on stability

255th National Meeting (2018)

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