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

In recent years,the self-assembly of surfactants containing flexible alkyl chains has been widely investigated.However,the investigation on the surfactants containing the rigid hydrophobic group is rarely reported.In this thesis,the dehydroabietic acid,which is the important derivative of rosin,was utilized as the starting material to synthesize surfactants with novel structures.Series of rosin-based surfactants containing rigid hydrophobic groups have been successfully prepared,and the self-assembly of which has been investigated in detail.The main results are summarized as follows:1.With the dehydroabietic acid as the starting material,a nearly totally rigid carboxylate surfactant containing an azobenzene group(R-azo-Na)was synthesized through seven steps.The structure and purity of the target product were identified with highresolution Mass Spectrum(HRMS),1H NMR and 13 C NMR spectrum.With 26 carbon atoms contained in the molecule,R-azo-Na still shows satisfied water solubility.The solubility of R-azo-Na is 88 mmol?L-1 at 25 °C.2.The aggregation behavior of R-azo-Na before and after UV light irradiation have been investigated by surface tension and fluorescence probe methods.The results showed that there was a significant aggregation discrepancy between trans-and cis-R-azo-Na isomers,verifing the advantage of a rigid surfactant in a photoresponsive system.trans-Razo-Na showed strong ability in stabilizing emulsions.The n-decane/water emulsion could be kept stable for more than 60 days by 0.5 mmol?L-1 R-azo-Na solution and exhibited good photoresponsive properties.In addition,trans-R-azo-Na can also form stable foams,the halflife t1/2 of which was 636,656,976,and 872 min for 0.3,1,2,and 4 mmol?L-1 trans-R-azoNa aqueous solutions,respectively.As revealed by the dynamic surface tension method,the presence of large adsorption barrier Ea for the adsorption/desorption of trans-R-azo-Na at the surface was responsible for the stability of foams formed by trans-R-azo-Na solutions.When the stable foams were irradiated with UV light,rapid rupture of the foams was observed,showing in situ responses to light.3.A series of rosin-based amino acid surfactants containing different flexible amino acid groups,abbreviated as R-6,R-6-2 and R-6-6,have been prepared with the dehydroabietic acid as the raw material.The structures of the final products were all identified with 1H NMR and high-resolution Mass Spectrum(HRMS).The surface activities of three surfactants were studied by surface tension and fluorescence probe methods.The results indicated that the aggregation of these surfactants was obviously improved with increasing the chain length of amino acid group.Three surfactants all have strong abilities to stabilize emulsions and foams.Among three surfactants,the half-life t1/2 of R-6-2 was as long as 2983 min.Thermodynamics of the micellization of three surfactants in aqueous solutions was studied by isothermal titration calorimetric(ITC)method.Entropy is the driving force in the micellar process.And the removal of water molecules plays a major role in the process.4.A quaternary ammonium Gemini surfactant,whose head groups was substituted by four hydroxyethyl groups,abbreviated as 12(2OH)-3-12-(2OH),was prepared.The effect of the rosin based amino acid surfactant R-6 on the liquid crystal behavior was investigated.12(2OH)-3-12(2OH)can form liquid crystals at relatively low temperatures with wide liquid crystal temperature region.Besides,this liquid crystal shows peculiar sustained-release behavior of phase enthalpy.With the addition of R-6,the polarized liquid crystal textures was depressed due to the increase of the system viscosity.However,the sustained-release behavior of phase enthalpy was still retained.The results provide a new pathway to modulate or develop complex fluids with rosin-based surfactants.