Assembly Systems At Gas-Liquid Interface From Surface-Active Particles Triggered By Metal Ions

Pickering foams have attracted wide attention due to their good stability and controllability.Once the solid particles are adsorbed on the gas-liquid interface,it is difficult to desorb because of the great desorption energy.At the same time,the interfacial films constructed by particles show strong rigidity,which can effectively inhibit film drainage and prevent the coalescence of bubbles.On the one hand,the focus of Pickering foams research lies in how to prepare surfaceactive particles by simple and convenient methods,so as to build a foam dispersion system with high stability.On the other hand,how to destroy the interfacial film is particularly important.Therefore,it is of great significance to build a stimuli-responsive Pickering foam system with solid particles and intelligent switching between foaming and defoaming.This paper has mainly carried out the following two works.In chapter 2,we successfully constructed pH-responsive Pickering foams by inducing amino acids to form surface-active particles with metal ions.Some hydrophobic amino acids,such as phenylalanine,leucine and tryptophan,can combine with Zn2+、Cd2+、Pb2+、Co2+ in their deprotonated forms to form particles with proper wettability,and Pickering foams could be further formed.The formation of Pickering foams was confirmed by optical microscope,FTIR,contact angle test and SEM.The foams exhibit good stability,and the reversible transition from foaming to defoaming can be realized by adjusting the pH value of the solution.When the pH value of the solution increases,amino acids exist in the form of anions,which are easy to coordinate with metal ions and form insoluble particles as stabilizers of foams.When the pH value decreases,the amino acids are protonated again,which makes the particles disappear,and finally leads to the defoaming of the system.In this work,a simple method for preparing Pickering foams from environmentally friendly amino acids was proposed,which provided a new idea for constructing a stimuli-responsive dispersion system.In chapter 3,perfluorocarboxylic acid can be induced to form hydrogels and foams by introducing metal ions.The formation mechanism of hydrogels or foams were investigated by optical microscope,FT-IR,SEM,contact angle test and XRD.The hydrogels are driven by metal coordination,hydrogen bonding,hydrophobic interaction and so on,while foams are stabilized by particles driven by coordination between metal ions and perfluorocarboxylic acid.The results show that the chain length of perfluorocarboxylic acid significantly affects the wettability of particles,and then affects the formation of foams.The foams systems can enrich the preparation methods of surface-active particles,and the foams exhibit good stability,which provides a reference for the preparation of three-phase flame retardant foams.