苯甲酸（1H－1，2，4－三唑－1－基）－3，3－二甲基－2－丁酮酯衍生物的合成

用冠醚作催化剂，通过苯甲酸盐同１－溴代－１－（１Ｈ－１，２，４－三唑－１－基）－３．３－二甲基丁酮－２－反应，合成了一系列苯甲酸（１Ｈ－１，２，４－三唑－１－基）－３，３－二甲基－２－丁酮酯类新化合物，并对合成方法进行了探讨。通过ＩＲ、￣１ＨＮＭＲ及元素分析，确定了化合物的结构。     

Transport phenomenon as a function of counter and co-ions in solution: chronopotentiometric behavior of anion exchange membrane in different aqueous electrolyte solutions

Anion exchange membrane has been investigated in different electrolyte solutions by chronopotentiometry to explore the influence of co-ion and counterion of the exchange group of the membrane, on the transport phenomena. Chloride, nitrate, sulfate and acetate in sodium salts were used as counterions and sodium, potassium, calcium and ammonium in chloride salts were used as co-ions. The membrane showed a potential drop (E₀) in all these electrolytes when a constant current was applied across it, which remained constant for a period less than τ, called the transition time and rose gradually to a maximum (E_max) value. The parameters such as τ, E₀ and E_max and the potential jump (ΔE) and τ and the inflection zone (Δt) along the time axis have been measured and compared at an applied current density (I) of 10 mA cm⁻² in 10 mM solutions. The values of τ^1/2/z_A[A₀] or τ^1/2/z_C[C₀], with or , E₀ and ΔE with or (where r_A and r_C are the ionic radii of counter and co-ions, respectively) have been correlated. Permselectivity (P) and transference number of the membrane with respect to each one of the above electrolytes have been evaluated and discussed.     

Chip‐Free Microscale‐Incubator‐Based Synthesis of Chitosan‐Based Gene Silencing Nanoparticles

The development of polymer‐based nanoparticles to ferry siRNA continues to evolve. It is becoming increasingly apparent that gene silencing nanoparticles produced by conventional bulk manufacturing techniques often exhibit physicochemical heterogeneity within and between batches that can affect the biological performance. Here a new facile and robust “chip‐free” method is presented, termed chip‐free agitation‐generated droplets (CAD) preparation, using chitosan‐based gene silencing nanoparticles as an example. The CAD‐prepared silencing particles, in comparison to the particles prepared by the conventional bulk protocol, exhibit lower surface charge (9 mV vs 21 mV at N/P = 5), higher stability (≈40% higher binding affinity and up to 30% less morphological deformation), and are less prone to aggregation measured by nanoparticle tracking analysis over a period of one month. Furthermore, these physical attributes contribute up to 19% higher in cell viability at N/P = 5, while the gene silencing of enhanced green fluorescent protein remains constant in a human cell line. Control of particle properties is necessary to advance siRNA‐based delivery; the CAD preparation represents a physical complement to chemical design modifications, which can be readily transferred among research labs and utilized for alternative polymer systems.     

Influence of polyelectrolyte and salt on the structure of dispersions containing charged colloidal particles

An integral equation theory has been used as the basis for studying the structure of dispersions containing charged colloidal particles: globular protein molecules with a nonzero dipole moment, a polyelectrolyte and a low-molecular salt. It is demonstrated that there is an effective attraction between charged colloidal particles, which increases in the presence of charged polymer chains. The influence of the length of polyelectrolyte chains and of salt concentration on the partial structure factor of colloidal particles was studied.     

Ultrasonic absorption spectroscopy between 5 and 3100 MHz on some aqueous polyelectrolyte solutions

The ultrasonic absorption coefficient has been measured as a function of frequency between 5 MHz and 3.1 GHz for aqueous solutions of polyacrylic acid and of its sodium, potassium, and tetraethylammonium salts. Unlike an aqueous solution of propionic acid, all polymer solutions clearly exhibit excess absorption. Within the frequency range under consideration the excess absorption spectra can be analytically represented by two Debye-type relaxation terms. At 25°C the corresponding relaxation times adopt values between 3 and 12.4 ns, and between 0.12 and 0.22ns, respectively. The former process is discussed in accordance with previous models. The relaxation of the polyacrylic acid solutions is assumed to be related to the formation of hydrogen bonds of the polymeric molecules and that of the polyacrylate solutions may be due to interactions of counterions with chain segments. The latter process, the existence of which has been first proven in this study, is likely to reflect rotational motions of carboxyl groups.     

The salt effect in the alkaline hydrolysis ofO-ethylO-(p-nitrophenyl) chloromethylphosphonate catalyzed by cetylpyridinium bromide

The alkaline hydrolysis ofO-ethylO-(p-nitrophenyl) chloromethylphosphonate catalyzed by the micelles of cetylpyridinium bromide is inhibited on addition of KCl, K Br, or sodium salicylate (NaSal). This is caused by both a decrease in the nucleophile concentration in micelles owing to a reduction in the surface potential and a change in the micellar structure and properties. Dedicated to the memory of Academician M. I. Kabachnik in connection with his 90th anniversary. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1922–1926, October, 1998.     

Thermodynamic properties of dilution of chondroitin 4-sulfate having tetraalkylammonium counterions

The dilution enthalpies, _dil H, of tetraalkylammonium chondroitin 4-sulfate (R₄NChSA) and polyacrylate (R₄NPAA) having methyl (Me), ethyl (Et), propyl (Pr) and butyl (Bu) as alkyl groups (R) were measured to elucidate the effects of hydrophobic counterions. The _dil H of R₄NChS-A and R₄NPAA were negative (exothermic) and decreased as the carbon number of tetraalkylammonium cation (R₄N⁺) increased. These results were found to possess the same effects on _dil H as these of bromides. The non-electrostatic terms of dilution enthalpies _dil H ⁿ of R₄NChS and R₄NPAA were evaluated by using the electrostatic terms of _dil H obtained from Manning's theory. The _dil H ⁿ of R₄NChS-A and R₄NPAA decreased, i.e., their exothermic tendencies increased as the carbon number of R₄N⁺ increased, and the rate of decrease of the R₄NPAA was more than that of the R₄NChS-A. These results are discussed in relation to the increase of the hydrated water structure around R₄N⁺ on dilution.     

New polycationic polynorbornene latexes bearing an amphiphilic sugar corona of counterions: synthesis and complexation with DNA

A new family of polycationic polynorbornene with ω-gluconamidoalkanoates and ω-lactobionamidoalkanoates as amphiphilic counterions has been prepared. These polymers spontaneously form stable latexes in water with an amphiphilic sugar corona around the particles. With these counterions, the sugar moieties are separated from the surface of latex particles by the aminoalkanoic acid residue and consequently are remote from the surface of such latexes. Such location of sugar may promote their stronger interaction with cell receptors. These original amphiphilic compartmentalized surface polycationic latexes are able to bind and efficiently complex DNA in very small complexes. Furthermore, because of the effect of the sugar corona on the formation of the complexes, there is only a slight influence of the hydrophobicity of the counterions on DNA packing.     

Phase behavior in mixtures of cationic and anionic surfactants in aqueous solutions

Phase behavior of cationic/anionic surfactant mixtures of the same chain length (n=10, 12 or 14) strongly depends on the molar ratio and actual concentration of the surfactants. Precipitation of catanionic surfactant and mixed micelles formation are observed over the concentration range investigated. Coacervate and liquid crystals are found to coexist in the transition region from crystalline catanionic surfactant to mixed micelles.The addition of oppositely charged surfactant diminishes the surface charge density at the mixed micelle/solution interface and enhances the apparent degree of counterion dissociation from mixed micelles. Cationic surfactants have a greater tendency to be incorporated in mixed micelles than anionic ones.     

Thermal Behavior of Nafion Membranes

The thermal behavior of Nafion-117 membranes was investigated by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). TG measurements revealed that the mechanism of thermal degradation of a Nafion membrane in the acid form is different from that of Nafion in the sodium form. The DSC curves for the first heating, for both acid and salt forms, display two endothermic peaks, near 120 and 230°C. The high-temperature peak was assigned to the crystalline domains melting in Nafion, and the low-temperature peak was attributed to a transition into ionic clusters, since this transition exhibits significant changes depending on the nature of the counterion and the degree of hydration.This revised version was published online in November 2005 with corrections to the Cover Date.