非离子-阴离子Bola型表面活性剂和纳米SiO2颗粒协同稳定的双重响应型O/W乳状液OACSTPCD

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.