Effect of pH and Oxygen Atom of the Hydrophobic Chain on the Self-Assembly Property and Morphology of the Pyridyl Boronic Acid Based Amphiphiles

Abstract

The surface activity and aggregation behavior of two synthesized boronic acid based anionic surfactants, sodium salt of 2-dodecyl pyridine-5-boronic acid (SDDPB) and sodium salt of 2-oxydodecyl pyridine-5-boronic acid (SODDPB), were studied in buffer solution at pH 9 and 13 containing carbohydrates. The self-assembly formation was investigated by use of a number of techniques including surface tension, conductivity, fluorescence spectroscopy, dynamic light scattering, X-ray diffraction, and transmission electron microscopy (TEM). Both of the amphiphiles exhibit a single break in the surface tension vs log(concentration) plots, indicating existence of one critical aggregation concentration. Steady state fluorescence spectroscopy was used to determine the polarity indexes using pyrene and the rigidity of the microenvironments of the aggregates using 1,6-diphenyl-1,3,5-hexatriene (DPH) as fluorescence probe molecules. The pKa's of both amphiphiles were determined in buffer solutions of different pH's. XRD studies were performed to shed light on the morphology of the self-assemblies. TEM micrographs revealed the existence of vesicles for both the amphiphiles in buffer solution of pH 9, but at pH 13, TEM pictures indicate the existence of closed vesicles in SDDPB solution and at concentrated solution the vesicles are fused to form sponge-like micelles. After aging the vesicular solution of pH 13 of SDDPB, the closed vesicles are destroyed. In contrast, for SODDPB at pH 13, TEM pictures suggest the existence of spherical and complex micelles in solution which were further transformed into crystal-like structure upon aging. The average hydrodynamic radii were determined by dynamic light scattering measurement. Therefore, for the first time, we have successfully synthesized two new surfactants containing pyridyl-boronic acid as a headgroup which shows remarkable tuning of morphology in two different pH's and in the presence of two different carbohydrates.

Phase Behavior and Aggregation in a Catanionic System Dominated by an Anionic Surfactant Containing a Large Rigid Group

“…Figure d shows the image of the middle phase of the AS3P of the C 14 ‐MPA‐Na (31 m m )/CTAB system. Interestingly, network structures are formed in this middle phase, and the meshes distributed in the micelles have various sizes, which demonstrates that sponge‐like micelles are formed . Figure e shows the image of the lower phase of the AS3P of the C 14 ‐MPA‐Na (31 m m )/CTAB system.…”

“…Interestingly,n etwork structures are formed in this middle phase, and the meshes distributed in the micelles have various sizes, which demonstrates that sponge-like micelles are formed. [48][49][50] Fig-ure 7e shows the image of the lower phase of the AS3P of the C 14 -MPA-Na (31 mm)/CTAB system. The micelles in this solution are similar to those in the lower phase of the ASTP,t hat is, they are spherical and rod-like micelles.T he Cryo-TEMi mage of the anisotropic homogeneous phase of the C 14 -MPA-Na (35 mm)/CTAB system shown in Figure 7f also reveals sponge-like micelles.…”

A New Class of Boronic Acid‐Derived Amphiphile‐Based Gel Emulsions Capable of Entrapping and Releasing Vitamin B12 and Doxorubicin

“…As the fructose is strongly binding carbohydrate of boronic acid, different amount of fructose (0.02‐0.5 M) was tested to solubilize the amphiphile at higher pHs and it was found that 0.5 M fructose was required to make the aggregate solution stable. The details of selecting proper solvent was given in our earlier publication . The pK a value of the amphiphiles were determined by steady state fluorescence anisotropy ( r ) measurements using DPH probe at buffer solutions of different pHs having 0.5 M fructose and at fixed concentration of the amphiphiles.…”

Synthesis and Insecticidal Activity of Fire Ant Venom Alkaloid-Based 2-Methyl-6-alkyl-Δ1,6-piperideines

“…All reactions were monitored by thin-layer chromatography on silica gel GF254 pre-coated plates (0.25 mm). The Grignard reagents n -C 11 H 23 MgBr, n -C 13 H 27 MgBr and n -C 15 H 31 MgBr were prepared according to a reported method from the corresponding n -alkyl bromide [ 43 ]. 1 H and 13 C NMR spectra were recorded on Varian Inova—400 MHz spectrometers using tetramethylsilane as the internal standard, and were reported in terms of chemical shift (δ ppm).…”