The Synthesis And Properties Of Imine Switchable Surfactants

The imine surfactant is a new kind of switchable surfactant, the system may be switchedbetween an aggregated, amphiphilic state and a nonaggregated, nonamphiphilic state by achange in pH or temperature, the dynamic nature of the system makes the structure highlyinteresting candidates for future smart drug-delivery vehicles. The imine QSAR propertieswere calculated by HyperChem software. By cluster analysis, it was differentiated whetherthe imine was a surfactant. Based on stepwise multiple regression, the obtained parameterswere taken as theoretical descriptors to establish the quantitation structure-propertyrelationship models for predicting surfactant activity. The predicted aldehyde Critical MicelleConcentration model included2parameters, namely Surface Area (Grid Van der Waals),refractivity. The correlation coefficient was0.99992and standard deviation was0.14007. Thepredicted imine Critical Micelle Concentration model included2parameters, namely SurfaceArea (Grid Van der Waals), polarizability. The correlation coefficient was0.99993andstandard deviation was0.06169. The predicted hydrodynamic diameters model included2parameters, namely Surface Area (Approx solvent-accessible), Volume(Gridsolvent-accessible)，The correlation coefficient was1and standard deviation was0.00346.These laid a good foundation for further study of the imine type surfactant. The predictedLogarithmic aldehyde Critical Micelle Concentration model included2parameters, namelySurface Area (Approx Van der Waals), solvent-accessible Surface Area (Grid Van der Waals).The correlation coefficient was0.9997. The predicted Logarithmic imine Critical MicelleConcentration model included2parameters, namely Surface Area (Approx Van der Waals),solvent-accessible Surface Area (Approx Van der Waals). The correlation coefficient was0.9839.With NaBH4the4-Hydroxymethylbenzaldehyde can be synthesised by reduction ofterephthalic aldehyde. The optimal conditions are: n(NaBH4):n(diald)=0.28:1, reacting for6hat0℃. The yield can be as high as98.03%. Followed by reaction of4-Hydroxymethylbenzaldehyde with NBS in the presence of PPh3,4-Bromomethylbenzaldehyde can be synthesize. The optima conditions are: n(ald)：n(PPh3):n(NBS)=1:1.2:1.26，reacting for0.5h at0℃，the yield is71%. Then we study themechanism of the reaction and presume that to be: Firstly, PPh3and NBS becomephosphonium positive ions and succinimide negative ions. Secondly, succinimide negativeions change to be succinimide by capturing proton from alcohol. Thirdly, Nucleophilicsubstitution between phosphonium positive ions and oxygen anions from alcohol is reactedand form intermediates containing P-O. Finally, the bromide ion attack the C-O, nucleophilicsubstitution occur to generate4-Bromomethylbenzaldehyde and PPh3O. The existence ofPPh3O prove the reaction mechanism to be true.4-methylbenzaldehyde, benzoyl peroxide and carbon tetrachloride were mixed andheated to reflux. NBS was added in1h and then refluxed for2h. After the reaction wascomplete, succinimide was collected by filtration, and carbon tetrachloride was removed bydistillation and the resulting mixture was purified by chromatography (silica gel.30/1petroleum ether/ethyl acetate) to afford4-Bromomethylbenzaldehyde as a white solid. Themolecule structure is analyzed by IR, melting point, LC-MS and NMR.4-Bromomethylbenzaldehyde and N(CH3)3solution were mixed and heated to reflux in CH2Cl2, the yield is93.56%. The imine surfactant is synthesized by mixture of the productand lauryl amine in pH=11.8phosphate buffer solution at25℃. The aldehyde Critical MicelleConcentration is2.2×10-5mol/L and the CMC is30.40mN/m, in acidic solutions, theproduct do not react with lauryl amine, the mixture show non-surfactant. A significantincrease in CMC was observed heating from25℃to65℃, the mixture lose surfactant upon55℃, indicating complete micelle dissociation. Using Nile Red as fluorescent probe, range thepH of the mixture from pH>10to pH <5, the maximum absorption wavelength of Nile Redchange from640nm to654nm, indicating imine surfactant is pH reversible.