Aqueous I2 Research Articles

Bisindole [3]arenes—Indolyl Macrocyclic Arenes Having Significant Iodine Capture Capacity

Bisindole [3]arenes—Indolyl Macrocyclic Arenes Having Significant Iodine Capture Capacity

Universal Intraductal Surface Antifouling Coating Based on an Amphiphilic Copolymer.

Surface modification on the inner wall of medical or industrial polymeric catheters with a high length/diameter ratio is highly desired. Herein, a universal and facile method based on an amphiphilic copolymer was developed to immobilize an intraductal surface antifouling coating for a variety of polymeric catheters. A fouling-repelled thin layer was formed by swelling-driven adsorption via directly perfusing an amphiphilic copolymer [polyvinylpyrrolidone-polydimethylsiloxane-polyvinylpyrrolidone (PVP-PDMS-PVP)] solution into catheters. In this copolymer, hydrophobic PDMS was embedded into a shrinking cross-linked network of catheters; also, PVP segments migrated to the surface under driving water to form a hydrophilic antifouling coating. Moreover, because of the coordination between I2 and pyrrolidone of PVP, the copolymer-modified intraductal surface was then infused with aqueous I2 to form the PVP-I2 complex, endowing this coating with bactericidal activity. Notably, diverse catheters with arbitrary shapes (circular, rectangular, triangular, and hexagonal) and different components (silicone, polyurethane, and polyethylene) were also verified to work using this interfacial interpenetration strategy. The findings in this work provide a new avenue toward facile and universal fabrication of intraductal surface antifouling catheters, creating a superior option for decreasing the consumable costs in industrial production and alleviating the pain of replacing catheters for patients.

Synthesis of oligodeoxynucleotides using the oxidatively cleavable 4-methoxytritylthio (MMTrS) group for protection of the 5′-hydroxyl group

We examined the synthesis of oligodeoxynucleotides containing all four nucleobases using the 4-methoxytritylthio (MMTrS) group for protection of the 5′-hydroxyl group. The MMTrS group could be introduced into 3′-O-TBDMS-deoxycytidine, -deoxyadenosine and -deoxyguanosine with the appropriate base protecting groups using strong bases such as n-butyl lithium and lithium hexamethyldisilazide. Because the MMTrS group could be removed by oxidation with an aqueous I2 solution, the oxidation of internucleotidic phosphite intermediates could be performed simultaneously. Thus, the nucleotide chain could be extended in a three-step protocol that comprised coupling, capping and oxidation/deprotection. Oligodeoxynucleotides with 10 and 20 mixed-base sequences could be synthesized using this protocol.

Temperature dependence of the equilibrium constant for iodine hydrolysis at temperatures between 25 and 120 °C

The equilibrium constant for iodine hydrolysis at elevated temperatures has been investigated using absorption spectroscopy and a simulation computer program. The temperature dependence of the aqueous I2 maximum extinction coefficient for visible light (at 460 nm) was first evaluated in a preliminary experiment using saturated I2 solution. The time dependence of I2 concentrations in dilute solution has subsequently been measured using the temperature-dependent extinction coefficient. The results were analysed by the simulation program, in which 11 normally accepted reactions were considered, and the equilibrium constant, K, was estimated. It was concluded that the K value at temperatures ranging between 25 and 120 °C may be expressed by log K(T)= 13880/T– 0.2445T+ 308.4 log T– 749.1, where the units of K and T are mol2 dm–6 and K, respectively.

Ternary diffusion with charged-complex formation in aqueous I2+NaI and I2+KI solutions

Diaphragm cells have been used to measure ternary diffusion coefficients for I2+NaI and I2+KI in aqueous solution at 25°C. Although most of the iodine molecules are bound to iodide ions and are transported as the triiodide species [I2(aq)+I−(aq)=I 3 − (aq)], diffusion of the iodide salts produces relatively small countercurrent coupled flows of the iodine component. The ternary diffusivity of the iodine component in the solutions is 10 to 20% larger than the diffusivity of the triiodide species. This behavior can be understood by considering electrostatic coupling of the ionic flows. The diffusion equations for I2+NaI and I2+KI components are reformulated in terns of NaI3+NaI and KI3+KI mixed electrolyte components.

Sorption and permeation of iodine in water‐swollen poly(vinyl alcohol) membranes and iodine complex formation

AbstractThe sorption and the permeation of iodine in water‐swollen poly(vinyl alcohol) (PVA) membranes and the formation of PVA–iodine complexes were studied. The logarithms of the permeability and the diffusion coefficient decreased approximately linearly with the increase in polymer volume fraction. When the membrane was soaked in an aqueous I2–KI solution, it contracted and Young's modulus increased. These findings were explained in terms of the formation of extra junction points due to the PVA–iodine complexes. These changes were reversible and could be recovered by replacing the solution with water. The length of the polyiodine chain increased with the increase in the degree of hydration of the membrane. At a fixed degree of hydration, Young's modulus of an iodine‐sorbed membrane was much greater than that of a membrane soaked in pure water. This finding was explained on the basis of a double‐network structure. The extension of the membrane promoted the complex formation, and the complex disappeared when the tension was released. The critical strain necessary for the complex formation was independent of the degree of hydration. The length of polyiodine chain increased with strain and became constant at higher strains.

Charge Injection into Organic Crystals: Influence of Electrodes on Dark- and Photoconductivity

Studies have been made of dark and photoconductivity in thin anthracene single crystals using a Ce4+ solution as one electrode and a 1MNaCl solution as the other electrode. It was found that the Ce4+ electrode was capable of injecting holes into anthracene in the dark, the saturation current at 15 000 v/cm being about 1 μa/cm2. This current was observed when the Ce4+ electrode was at a positive potential. With the same polarity, it was found that there was practically no increase in the saturation current upon illumination of the crystal with 3650 or 4300 A light; at low voltages there was a distinct photoeffect which was attributed to the emptying of polarization producing traps, thus increasing the internal field. The saturation current was proportional to the sixtenths power of the Ce4+ concentration. At low voltages, the current was very small until a certain voltage, referred to as the onset voltage, was reached, after which the current increased rapidly. The onset voltage was larger for the dark current than for the photocurrent. The efficiency of carrier production by the Ce4+ ion was about 10—10 based on a simple collision hypothesis. Possible explanations for this low efficiency were advanced but no definite mechanism was chosen. The use of Ce3+ ion was without effect in increasing either the dark or photocurrent. Using a positive electrode of I2 in glacial acetic acid, it was found that there was practically no hole injection, in contrast with the marked hole injecting characteristics of the aqueous I2–I— electrode. Furthermore, the Ce4+ and I2–I— electrodes were ineffective with naphthalene. These results are explained by reference to a criterion for hole injection IA—WE—Ex<0, where WE is the work function of the electrode, IA is the ionization energy of anthracene in the solid, and Ex is the externally supplied energy (optical, thermal, electric field).