Dual-responsive oil-in-water emulsions co-stabilized by a nonionic-anionic Bola surfactant and silica nanoparticles
A smart nonionic-anionic Bola surfactant was synthesized which could be switched between nonionic form CH3O(EO)5-R11-COOH(pH<p Ka= 6.6)and Bola form CH3O(EO)5-R11-COONa(pH>p Ka)as triggered by pH.Individually,the nonionic/Bola forms behaved as poor/good emulsifiers,respectively.When the nonionic form was mixed with silica nanoparticles,they could co-stabilize n-decane-in-water Pickering emulsions,where the silica nanoparticles were hydrophobized in situ to be surface-active by adsorption of the surfactant via hydrogen bonding.The Pickering emulsions could be switched between stable and unstable statuses many times as triggered by either pH or temperature.On the other hand,the Bola form could co-stabilize oil-in-dispersion emulsions with silica nanoparticles,which were resistant to heating but were sensitive to the salt formed during pH alternation.However,in contrast to the CH3(EO)7-R11-COONa which could completely transfer to aqueous phase after demulsification,its analogue with shorter EO chain,i.e.,CH3(EO)5-R11-COONa,was still partially oil-soluble either in nonionic form or in bola form,suggesting a significant effect of EO number on the performance of these novel smart surfactants.
nonionic-anionic Bola surfactantsilica nanoparticlePickering emulsionpH-responsivetemperature-responsive
国家科技期刊平台
NSTL
万方数据
维普
