Study On The Synthesis And Self-assembly Of Rosin-based Oligomeric Surfactants

Innovations in surfactant structure are a feasible way to probe molecular self-assembly principles.The oligomeric surfactants received widely attentions in recent years because of their rich and novel aggregation morphologies.However,the hydrophobic groups of investigated oligomeric surfactants are mostly alkyl chains.The investigation of oligomeric surfactants with rigid hydrophobic groups is rare up to now.In this thesis,the dehydroabietic acid,an important drivative of rosin,was taken as the starting material.Series of rosin-based oligomeric surfactants were successfully synthesized,and the self-assembly of surfactants has also been investigated.The main contents are summarized as follows:?1?Using the dehydroabietic acid as the raw material,a series of novel Gemini?dimeric?surfactants,abbreviated R-?EO?_n-E-R?n=1,2,3?,were synthesized.Surface tension method,fluorescent probe method,conductivity method and isothermal titration calorimetry?ITC?method were used to investigate the surface activities.At 25?C,the cmc value of R-?EO?_n-E-R?n=1,2,3?is 0.45 mmol·L^-1,0.57 mmol·L^-1 and 0.44 mmol·L^-1,respectively,and the minimum molecular occupation area(A_min)at the air/water interface is 1.05 nm²,1.18 nm² and 1.21 nm²,respectively.At low concentrations,R-?EO?_n-E-R?n=1,2,3?form micelles with an aggregation number of approximately 10.Besides,these surfactants all have strong abilities in stabilizing emulsions and foams.?2?The viscoelastic properties and aggregation morphology of R-?EO?-E-R solutions have been investigated by rheology,freeze-fracture transmission electron microscopy?FF-TEM?,cryogenic transmission electron microscopy?Cyro-TEM?and fluorescent probe methods.As the concentration increases,R-?EO?-E-R without any additives forms wormlike micelles,endowing the solutions with an obvious viscoelasticity.Further increases in the concentration lead to the coexistence of single-walled vesicles,double-walled vesicles and rarely observed long,tubular vesicles.These behaviors are attributed to the two large,rigid hydrophobic groups of R-?EO?-E-R.The research of this system lays the foundation for the exploration of novel self-assembly behavior of surfactants.?3?A star-shaped trimeric cationic surfactant?R-4-ben?was synthesized by combining the bulk-mass dehydroabietic units and phenyl.The solubility and surface activity of R-4-ben were firstly investigated.R-4-ben has excellent solubilities in weak polar solvents.A hydrogel with high elasticity was formed by R-4-ben and a lipophilic nonionic surfactant C₁₂EO₃.The polarizing optical microscope?POM?,small angle X-ray scattering?SAXS?and rheological methods were used to investigate the aggregation behavior of R-4-ben/C₁₂EO₃/Water systems.The systems can form lamellar liquid crystal phase at extremely low surfactant concentrations.The investigation of R-4-ben/C₁₂EO₃/Water system is expected to contribute to the construction of novel hydrogel system.