The coalescence of two millimeter-sized n-dodecane droplets grown at pH 10 in the presence of lightly cross-linked 260 nm diameter charge-stabilized poly(tert-butylamino)ethyl methacrylate (PTBAEMA) latexes was monitored using a high-speed video camera. n-Dodecane was investigated as an oil phase in the absence and presence of an oil-soluble cross-linker (tolylene 2,4-diisocyanate-terminated poly(propylene glycol), PPG-TDI). In the absence of PPG-TDI, rapid coalescence was observed for giant PTBAEMA-stabilized Pickering oil droplets. An increase in the damping coefficient for coalescing PTBAEMA-stabilized n-dodecane droplets (compared to that for bare oil droplets) indicated PTBAEMA latex adsorption at pH 10. Addition of PPG-TDI cross-linker to the oil droplets led to a reduction in the interfacial tension, confirming the surface-active nature of this reagent. PPG-TDI was added to the oil phase to react with the secondary amine groups on the PTBAEMA latex, producing giant colloidosomes that were stable to coalescence when brought into contact. This was not observed for bare oil droplets in the presence of PPG-TDI, confirming that the cross-linked latex particles at the interface provide the additional stability towards coalescence. Separation of the colloidosomes five minutes after their contact produced a visible 'neck' connecting the droplets. Subsequent separation of the n-dodecane-based colloidosomes merely stretched the interfacial contact area, indicating formation of inter-crosslinked colloidosomes. Asymmetric interactions between a Pickering droplet and a colloidosome were also examined. The effect of adding PPG-TDI cross-linker to only one droplet resulted in �arrested coalescence� behaviour in the presence of PTBAEMA latex particles at pH 10. In this context, the droplet aging time was found to be critical. Aging times of less than 60 s led to droplet coalescence, whereas aging times longer than 60 s indicated cross-linker diffusion from one droplet to the other, which produced inter-crosslinked colloidosomes. Arrested coalescence was only observed for intermediate aging times of approximately 60 s.

Coalescence behavior of giant Pickering droplets and colloidosomes stabilized by poly(<i>tert</i>-butylaminoethyl methacrylate) latexes

248th National Meeting (2014)

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Coalescence behavior of giant Pickering droplets and colloidosomes stabilized by poly(tert-butylaminoethyl methacrylate) latexes