Synthesis And Properties Of Oligomeric Surfactants

Compared with traditional monomeric surfactants,oligomeric surfactants exhibit much better performance,such as higher surface activity,lower critical micelle concentration,and more diverse aggregate structures.To explore the superior properties of oligomeric surfactants is necessary,and it will be possible to bridge the gap between gemini surfactants and polymeric surfactants.Meanwhile,surfactant-polymer system is widely used in cosmetics,pharmaceuticals,detergents,paints,tertiary oil recovery and other industries.It was found that surfactant-polymer system acquired new properties,which attributes to the mix of surfactant and polymer,and it will enhance the performance of polymer.Therefore,the research on the interaction between surfactant and polymer has both important theoretical and applied values.One kind of dendritic octamer cationic surfactants?DOCS?was synthesized,and IR spectroscopy and element analysis were used to characterize the structure and composition of products.Aggregation behavior of DOCS was explored systematically by surface tension,conductivity,steady-state fluorescence measurements,UV absorption spectroscopy and shear rheology.The critical micelle concentrations?CMC?of C₁₂-DOCS and C₁₄-DOCS are 0.8mmol/L,0.2 mmol/L separately.Compared with conventional single-chain surfactants,C₁₂-DOCS and C₁₄-DOCS have high efficiency and ability to reduce the surface tension.C₁₄-DOCS has stronger adsorption capacity in the gas-liquid interface than C₁₂-DOCS has.The micellization process of DOCS is entropy-driven.The critical micellar aggregation number of DOCS is 13.With the change of the concentration of DOCS,the micellar shape has transformed from rods into entangled long worms.With the change of the shear rate,the micelles have entangled into a network structure.DOCS/HPAM mixtures have been investigated by steady-state fluorescence,turbidity measurements and rheological method.At low HPAM concentration,there is no interaction between them.At higher HPAM concentration,the interaction between DOCS and HPAM in aqueous solution becomes more complicated.First,DOCS molecule monomers bound to the HPAM backbone driven by electrostatic interactions.DOCS/HPAM formed mixed micelle through the hydrophobic force along with the increasing DOCS molecule monomers binding to HPAM chains.Formation of multichain complexes causes a size increasing.However,the size of the complexes reaches a certain value,partial collapse of the polyelectrolyte chains,leading to a size decrease.At last,increasing DOCS concentration,the free micelles only containing DOCS molecules.