Study On Synthesis,Properties And Application Of Gemini Surfactants With Amide And Ester Groups

Owing to their unique structures like the existence of spacer groups,Gemini surfactants exhibit superior performance compared with traditional surfactants.They have attracted increasing interests for fundamental research and industrial applications.The introduction of ester and amide groups in surfactants endows them with low toxicity,low irritation,and good biodegradability.Thus,introducing ester and amide groups into Gemini surfactants not only enhances their surface activity,but also provides good degradation properties.This meets with the concept that lucid waters and lush mountains are invaluable assets in China.As a result,a series of diester amide cationic gemini surfactants were synthesized,with phenyl ring structures introduced into the spacer group to explore their aggregation behavior and properties.The main content and of this study are as follow:A series of cationic Gemini surfactants with different hydrophobic chain lengths,C_n-E₂Ph-C_n（n=12-16）,were synthesized through a three-step reaction using fatty acid,3-dimethylaminopropylamine,resorcinol,and chloroacetyl chloride as the raw materials.The structures of the obtained surfactants were characterized using FT-IR,MS,and ¹H NMR.The Krafft points of the surfactants were found to be below 0°C,indicating good water solubility.The surface activity of C_n-E₂Ph-C_n was determined using surface tension,conductivity,and steady-state fluorescence probe methods,and relevant parameters were calculated.With the increase of the hydrophobic chain length,the critical micelle concentration（cmc）of C_n-E₂Ph-C_n at 25°C decreased,while the surface tension at the cmc(γ_cmc)increased.The thermodynamic parameters for micellization of C_n-E₂Ph-C_n in water were calculated using conductivity measurements,suggesting the micellization process was spontaneous and exothermic,driven by entropy.The aggregate size of the micelles in C_n-E₂Ph-C_n aqueous solutions was determined using steady-state fluorescence quenching.It is revealed the aggregate size decreases with increasing hydrophobic chain length.Moreover,as confirmed by dynamic light scattering,the micelles exhibit a spherical shape.Compared to traditional surfactants,C_n-E₂Ph-C_n showed superior foamability,wetting ability,emulsification,and anti-static properties in performance testing.To develop an environmentally friendly hair dye,the present study investigated the interactions among the target product,polyethylene glycol（PEG）,and sodium alginate（Na Alg）in the formulation system.The interactions between C_n-E₂Ph-C_n and these two compounds were studied using surface tension,turbidity,and micro-polarity methods.No significant interaction was found with PEG,whereas a strong interaction was observed with Na Alg.The surface tension curve exhibited a"double inflection point"phenomenon,indicating the prepared gemini surfactant was adsorbed onto the polymer main chain via electrostatic attraction,forming a pearl-necklace-like composite structure.The adsorption behavior between the two compounds changed with the addition of Na Cl,resulting in two effects,namely salt-enhanced and salt-attenuated effects,depending on their competition at different concentrations.Finally,the hair dyeing effects of different surfactants on Yak wool were compared,revealing that the addition of surfactants affected the color characteristics of the dyed hair,and cationic surfactants improved the tensile strength of Yak wool.The dyeing formula containing C₁₂-E₂Ph-C₁₂ and sodium alginate exhibited good stability and coloring effects.A smart temperature-sensitive cold perm agent was prepared in this study to reduce the damage of the active ingredient（sodium thioglycolate）to the human body.The agent remains liquid at room temperature and undergoes gelation upon contact with the scalp（usually at32°C）,transforming into a semi-solid gel state.The addition of sodium thioglycolate caused gelation at room temperature,failing to fill the desired goal.The gelation temperature was increased after the addition of the target product,and can be controlled by adjusting the ratio of the control agent.The invitro release and transdermal absorption behaviors of sodium thioglycolate aqueous solution,ordinary cold perm agent and composite agent were systematically compared at 32°C.The release behavior was studied by HPLC.The results showed that the in vitro release behavior of the composite agent followed a composite first-order kinetic model,and after 1 h of transdermal experiment,the amount of transdermal absorption was only 500μg·cm^-2,while that of sodium thioglycolate aqueous solution was1400μg·cm^-2.Compared with other formulations,it had good sustained-release effect.Due to the interaction of hydrophobic chains,the sustained-release effect gradually increased with the lengthening of carbon chains.The formula is desired to become a new cold perm agent with high safety.