Volume 55, Issue 3

The mesomorphic, morphologic and optical refracting properties of the bicomponent amphiphilic lyotropic systems have been investigated. Five amphiphiles with various concentration combinations as cationic – cationic, anionic – anionic and cationic – anionic lyotropic mixtures have been used for preparation of lyotropic systems. The mixtures were prepared with a constant (amphiphile1 + amphiphile2)/water concentration ratio. Isotropic lyotropic phase and hexagonal and lamellar lyotropic mesophases have been found in lyotropic systems under investigations. Dynamics of change of the magneto-morphologic properties vs. time, character of the heterophase regions of the mesophase – isotropic liquid phase transitions and temperature dependencies of the optical refracting properties of these bicomponent amphiphilic lyotropic systems have been investigated.

In this study, ZnO nanoparticles were synthesized from Zn(OAc) 2 · 2H 2 O and NaOH in 2-propanol. Nucleation and growth are fast, and hence at longer times the particle size is controlled by coarsening. The optical properties were investigated as a function of time. X-ray diffraction (XRD) also has been used to characterize ZnO nanoparticles. The wavelength onset (λ ons ) of the absorption spectra was used to estimate the particle size. The effect of the temperature and the surfactant on the growth process of ZnO nanoparticles was followed by UV-Vis spectrophotometer using the effective mass model. Particle growth was fitted using the commonly used linear coarsening model. The linear coarsening model is applied to calculate the rate constant of growth of ZnO nanoparticles. In all cases the linear coarsening produced good fits of the data. The results reveal that the temperature and the CTAB concentration play an important role in growth process of ZnO nanoparticles.

The effects of sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB) and Brij 35 on the oscillations of the cerium-catalyzed Belousov-Zhabotinsky (B-Z) reaction with ninhydrin as the organic substrate at 30 °C were described by following the change in absorbance of the reaction mixtures at 357 nm. The behavior of the oscillatory parameters was determined: (i) the induction period (IP) increases first and then decreases with increasing the concentration of all used surfactants (ii) the number of oscillations decreases with the SDS concentration, while for Brij 35 and CTAB it remains nearly constant, and (iii) the mean amplitude of the oscillations decreases with increasing concentration of CTAB and SDS, while it varies irregularly with that of Brij 35. The ability of micelles to selectively shield ions and molecules may explain their effect on the oscillation parameters of the studied B-Z system.

The ambient solubility of the mineral salts NaCl, KCl, CsCl, KBr, K 2 SO 4 and CuSO 4 is reported as a function of composition of mixed binary solvents consisting of water with polyethylene glycol (PEG 200), ethoxylated C 9–11 alcohols (C 10 E 6 ) and ethoxylated, or propoxylated C 10–12 alcohols (C 11 E 6 P 1 ). Solubility gradually decreases with decreasing water content and follows the order PEG 200 > C 10 E 6 > C 11 E 6 P 1 . Solubility of CsCl and KBr was found to be surprisingly high in neat PEG 200, on the order of 1 mol kg −1 , and in neat C 10 E 6 , on the order of 0.1 mol · kg −1 . The observed solubility trends are explained by the theory of hard and soft acids and bases under the consideration of the polarity of the surfactants.

The present study deals with the solubility enhancement of the two polycyclic aromatic hydrocarbons (PAHs) anthracene and pyrene in the aqueous micellar system of the cationic ester-containing cleavable gemini surfactant ethane-1,2-diyl-bis(N,N-dimethyl-N-tetradecylammoniumacetoxy) dichloride (14-E2-14 = C 14 H 29 (CH 3 ) 2 N + (CH 2 COOCH 2 ) 2 N + (CH 3 ) 2 C 14 H 29 · 2Cl − )), and its equimolar binary mixtures with some typical conventional cationic, anionic and non-ionic surfactants. The surface tension and conductivity measurements were used to evaluate the physicochemical parameters such as the critical micelle concentration ( CMC ), the interaction parameter ( β m ) and Gibbs excess free energy of micellization (Δ G ex m ) of the systems. The extent of solubilization of the micellar systems towards PAHs has been quantified in terms of molar solublization ratio ( MSR ), micellar/water partition coefficient (ln K m ) and the standard Gibbs free energy of solubilization (Δ G s 0 ). Above the CMC, all studied single as well as binary gemini-conventional surfactant systems show an increase in solubilization of the PAHs. For pure systems, the MSR value of Brij 58 was found to be significantly higher than that of the other amphiphiles. Amongst the mixed surfactant systems, the solubility enhancement of anthracene is found to be maximum in the 14-E2-14 + SDS/SDBS system whereas the system14-E2-14 + Brij 58 shows a higher solubility for pyrene.

Novel non-ionic gemini surfactants derived from carbohydrate carrying two hydrophobic tails with varying tail length of C 12 , C 14 and C 16, two sugar moiety as head groups, and an α-(CH 2 ) 6 -flexible spacer have been synthesized. The head group of these gemini surfactants consists of sugar moiety connected to C-6 of tertiary amines. These gemini amphiphiles were explored as reverse micellar systems for encapsulation of some D- and L-enantiomers of aromatic α-amino acids i.e. histidine (His), phenylalanine (Phe), tyrosine (Tyr) and tryptophan (Trp) in n -hexane in the absence of water. It is found that these amino acids are encapsulated in the order of His > Phe > Tyr > Trp, and it is also observed that in almost all cases the D-enantiomers were better encapsulated as compared to the L-enantiomers. In all cases, encapsulation of D- and L-enantiomers of aromatic α-amino acids increased with increase of the hydrophobic chain length of the gemini surfactants.

The photo-responsive ionic liquid surfactants 4-Butylazobenzene-4′-(oxyethyl)methylimidazolium with Br − (AZMIMBr) and BF 4 − (AZMIMBF 4 ) counterions were synthesized, and their structures were characterized by means of 1 H NMR. Their properties for pre- or post-UV irradiation were investigated by employing tensiometry, electrical conductance, thermal gravimetry-differential scanning calorimetry (TG-DSC) and small-angle X-ray scattering (SAXS). The effect of UV irradiation time on photoisomerization of two surfactants solutions was evaluated, which showed the photoisomerization efficiency decreases with an increase of their concentrations. After UV irradiation, the CMC value of the two surfactants increased, whereas, the surface tensions at CMC (γ CMC ) and the fraction of counterion binding (β) were approximately the same. SAXS coupled with polarized optical microscopic studies (POM studies) confirmed that the liquid crystal textures of AZMIMBr could be affected by UV-irradiation. The detailed analysis of thermodynamic parameters revealed that the micellizaton of AZMIMBr was entropy-driven, and the micellization of AZMIMBF 4 was enthalpy-driven.

The cationic surfactant, N-(3-octadecylamino-2-hydroxyl) propyl trimethyl ammonium chloride was synthesized by an improved synthesis method and the structure was confirmed by Mass Spectrometry and 1 H NMR Spectrometry. The physiochemical properties of the product were investigated systematically by surface tension and conductivity measurements. Various physiochemical parameters were calculated to evaluate the surface activities of the surfactant. The results show that both the critical micelle concentration and the degree of counterion dissociation increased with increasing temperature, but the surface tension at CMC decreased, which is opposite to that obtained on the previous condition with increasing NaCl concentration. The thermodynamic parameters obtained from conductivity measurement show that the micelle formation of the surfactant is entropy-driven in the investigated temperature range. While used as an asphalt emulsifier, N-(3-octadecylamino-2-hydroxyl) propyl trimethyl ammonium chloride exhibited an excellent emulsifying ability and it was a medium-set asphalt emulsifier.

Series of cyclic polyethylene glycol succinates based surfactants bearing a hydro- or fluorocarbon group was synthesized and characterized. Evaluation of the surface-active properties of the obtained compounds reveals, (i) the surface tension decreases gradually when is the length of the lipophilic chain increased (ii) the critical micelle concentration (CMC) increases with the number of ethylene oxide unit present in the polar head and (iii) surface tension follows the increasing pattern of hydrophilic-lipophilic balance (HLB) number.

Ultra-low interfacial tension (IFT) is an important parameter for selecting surfactants to apply in chemical enhanced oil recovery (CEOR). In this study, the IFT between the solution of the surfactant ANSM and Dagang crude oil was measured using the spinning drop method. The effects of the surfactant concentration, temperature, salt types and aging time on the IFT were investigated in detail. The results showed that ANSM effectively reduced the IFT without alkali. Ultra-low IFT was formed in a wide range of surfactant concentrations from 0.05∼ 0.5 wt.% and a wide range of temperatures from 20∼80°C. In addition, ANSM also showed great NaCl tolerance, with a maximum NaCl concentration of 130000 mg · L − 1 . Furthermore, 0.1 wt.% ANSM maintained an ultra-low IFT, even with 900 mg · L − 1 CaCl 2 or 1300 mg · L − 1 MgCl 2, in the presence of 10000 mg · L − 1 NaCl. ANSM also had an excellent stability; the solution maintained the ultra-low IFT for 60 days at 90°C. Thus, ANSM proved itself as a potential candidate for CEOR.