Dielectric spectroscopy study of low-concentration aqueous solutions of a calix[4]resorcinarene derivative (original) (raw)
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Russian Chemical Bulletin, 2015
The solubilization capacities of binary systems based on cationic surfactants (cetyltrimethyl ammonium bromide and dodecanediyl 1,12 bis(hydroxyethylmethylhexadecylammonium bromide)) and new amphiphilic calix[4]resorcinol with amino acid residues at the upper rim and alkyl substituents at the lower rim with respect to the spectral probe Sudan I and the fluorescent labels (pyrene and prodan) were studied by spectrophotometry and fluorimetry. Critical aggregation concentrations were determined and aggregation numbers were calculat ed. The sizes of surfactant-calix[4]resorcinol complexes were determined by dynamic light scattering.
2010
Self-organization of amphiphilic calixarenes oxyethylated at a lower rim has been investigated in water and water-organic solutions. In the range of isotropic solutions three types of structural transitions were indicated by a complex of methods. The first critical point indicated by surface tension, dynamic light scattering and atomic force microscopy methods is probably connected with the formation of "infinite" organized structures (of hundreds nanometers in size) through the open association model. This aggregative phenomenon covers the concentration range below 10 −3 M. In the case of aqueous calixarene solutions these large aggregates co-exist with small micelle-like particles and undergo a rearrangement with an increase in the concentration. The second structural transition occurs beyond 10 −3 M. It is revealed in aqueous calixarene solutions by surface tension, spine probe, viscosimetry and dynamic light scattering methods. Small aggregates (∼10 nm in diameter) are formed in this range through a closed model typical for conventional surfactants. The third transition indicated by viscosimetry and in single case by tensiometry can be connected with an elongation of aggregates. The polarization microscopy and X-ray diffraction studies reveal the anisotropic behavior with the concentration of solutions. Parameters of the existence of liquid crystalline mesophases are found to be influenced by the structure of substituents at both the upper and lower rims, as well as by the nature of solvent.
Monolayer behavior of calix-4-resorcinarenes and their surfactant complexes
Thin Solid Films, 2012
We describe within this paper a series of calix-4-resorcinarenes along with their complexes with tetraalkylammonium surfactants and their behavior in Langmuir monolayers. Calix-4-resorcinarenes were synthesized containing both undecyl and phenyl sidechains and then modified using Mannich reactions to incorporate neutral, cationic or anionic groups in the 2-positions of the resorcinol unit. In the cases of resorcinarenes modified with four sulfonate groups, mixing with long chain dialkyl dimethyl ammonium surfactants led to the formation of 1:4 complexes. These various materials were spread as Langmuir monolayers and their behavior upon compression measured. Long chain substituted resorcinarenes gave more stable monolayers than their short chain analogues. The incorporation of long chain surfactants led to large increases in surface area, demonstrating that both resorcinarenes and surfactant are located at the water surface, except for one system where a bilayer structure is potentially formed.
Vesicle-to-micelle transition in aqueous solutions of amphiphilic calixarene derivatives
Physical review. E, Statistical, nonlinear, and soft matter physics, 2006
Structure and conformation of spontaneous self-assembled calix[8]arenes derivatives are studied by means of static and dynamic light scattering and electrophoretic mobility. These amphiphilic molecules are in the aggregated form in aqueous solution, in a wide range of pH; they take a vesicle structure in neutral and basic pH environment, but, in relatively strong acidic conditions (below pH=4.5), a transition from vesicle to micelle occurs. The structural change is driven by the surface charge density. At neutral pH calix[8]arenes take a negative surface charge, which prevents coagulation and ensures stability; at acidic pH the surface charge tend to become positive because of the protonation of the hydrophilic head. These pH-responsive aggregates, able to release an encapsulated hydrophilic guest, are promising systems for application as nanocarriers.
Langmuir and LB properties of two calix[4]resorcinarenes: Interactions with various analytes
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2008
The ability of calixarene based molecules to interact with amino acids has been the basis of many studies. The Langmuir and LB properties of two calix[4]resorcinarenes have been investigated. The properties of the layer formed at the air-water interface were studied by surface pressure area isotherms. LB deposition onto glass substrates has shown that multilayer assemblies can be built up. The UV-visible spectra of resulting LB films have been recorded, indicating that the compounds are coloured as a result of intra-molecular charge transfer bands. The sensitivity of the surface pressure area isotherms has been investigated in relation to the exposure to various analytes delivered from the subphase (i.e. amino acids). Furthermore, exposure of the LB films to a wide range of vapours (e.g. amines, alcohols, thiols) has led to modified UV-visible spectra.
Macroheterocycles, 2017
The intermolecular interaction of azobenzenesulfonate calix[4]arene with cationic surfactant CTAB was studied by a complex of physicochemical methods. The influence of calix[4]arene:CTAB ratio on the form of the aggregates in their mixed composition in the aqueous medium was determined. Single-layer vesicles are formed in the equimolar azobenzenesulfonate calix[4]arene-CTAB mixture. A threefold increase in the proportion of CTAB leads to the enlargement of vesicles, namely, an increase in numbers of bilayers. Spectrophotometry was used to select the conditions for binding of the hydrophobic spectral probe Sudan I by this mixed composition. The fluorescence spectroscopy establishes dependence between the amount of encapsulated Rhodamine B and the size of the vesicle. Thus, the azobenzenesulfonate calix[4]arene-CTAB system is capable for binding of both hydrophobic and hydrophilic substrates depending on the components ratio.
2015
Abstract: Among different types of calixarenes, the water–soluble ones are of especial interest because of their possible applications in biochemical research. In order to elucidate the nature of aqueous solutions of a cationic amphiphilic calixarene, substituted tetrapropoxy-calix[4]arene bearing hydrophilic choline groups at the upper rim, we studied vis– spectroscopically the influence of the above system on the acid–base behavior of three indicator dyes, namely, 2,4-dinitrophenol, bromophenol blue, and N,N/-dioctadecylrhodamine, at constant ionic strength of 0.05 M, maintained with NaCl addition. Simultaneously, ‘apparent ’ ionization constants, aaK, of the same dyes were determined in the presence of common cationic surfactant micelles. Within the concentration range from 1.0×10–5 to 0.01 M, the aforementioned water–soluble calixarene displays effects similar to those of micelles of cetyltrimethylammonium bromide (or chloride). The shifts of the absorption and emission bands in...