Shear banding in strained semicrystalline polyamide 6 films as revealed by atomic force microscopy: Role of the amorphous phase

Atomic force microscopy (AFM) has been used to visualize the plastic deformation mechanisms that are responsible for the yielding of semicrystalline polymers of low degree of crystallinity (<50%). Indeed, AFM, if operated in suitable conditions, is able to image both the amorphous and the crystalline phases. Polyamide 6 films have been drawn at temperatures T < 160 °C. Postmortem AFM observations show that, at yield, shear bands nucleate and propagate in the amorphous phase. They cross the crystalline lamellae and run over the whole surface of the sample. By crossing the lamellae, they form nanoblocks of uniform size. Neither the size of the nanoblocks nor the angle between the tensile axis and the shear bands can be explained in terms of crystal plasticity. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 687–701, 2004     

Structure and properties of the mesophase of syndiotactic polystyrene. VIII. Solvent sorption behavior of syndiotactic polystyrene/p‐chlorotoluene mesophase membranes

A crystalline δ form of a syndiotactic polystyrene (sPS) membrane was prepared from a solution of sPS (1 wt %) and p‐chlorotoluene (p‐CT) by a solution‐casting method. The mesophase (δ empty form) of sPS was obtained by the extraction of the guest solvent from the δ form of sPS by a stepwise solvent‐extraction method. The sPS/p‐CT mesophase membrane [p‐CT (A‐M)] was used for the sorption of 1 mol % p‐CT for different times and for the sorption of different concentrations of p‐CT, chlorobenzene (CB), p‐xylene (p‐X), toluene, and chloroform for 48 h. The presence of solvents in the sPS membrane was confirmed by IR analysis. A thermal study revealed that the sorption amount of 1 mol % p‐CT increased with increasing immersion time, and the sorption amounts of different solvents increased with increasing solvent concentration. Differential scanning calorimetry results showed that the desorption peak temperature increased as the amount of the solvent increased in the clathrated sPS membrane. Wide‐angle X‐ray diffraction results showed that 2θ at 8.25° was slightly shifted toward 8°, and there was no change in the peak position at 10° for p‐CT (A‐M), which was immersed in different solvents (1 mol %); however, the intensity of 2θ at 10° was not similar for all the samples. Among the solvents used for the sorption studies at 1 mol %, p‐CT (A‐M) could sorb more p‐CT and CB than p‐X, toluene, and chloroform. The solvent sorption isotherm was the Langmuir sorption mechanism. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3439–3446, 2004     

Dynamic surface tension measurements of surfactant solutions using the maximum bubble pressure method – limits of applicability

One of the essential differences in the design of bubble pressure tensiometers consists in the geometry of the measuring capillaries. To reach extremely short adsorption times of milliseconds and below, the so-called deadtime of the capillaries must be of the order of some 10 ms. In particular, for concentrated surfactant solutions, such as micellar solutions, short deadtimes are needed to minimize the initial surfactant load of the generated bubbles. A theoretical model is derived and confirmed by experiments performed for a wide range of experimental conditions, mainly in respect to variations in deadtime and bubble volume.     

A sequential injection system for the spectrophotometric determination of calcium, magnesium and alkalinity in water samples.

A sequential injection methodology for the spectrophotometric determination of calcium, magnesium and alkalinity in water samples is proposed. A single manifold is used for the determination of the three analytes, and the same protocol sequence allows the sequential determination of calcium and magnesium (the sum corresponds to the water hardness). The determination of both metals is based on their reaction with cresolphtalein complexone; mutual interference is minimized by using 8-hydroxyquinoline for the determination of calcium and ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) for the determination of magnesium. Alkalinity determination is based on a reaction with acetic acid, and corresponding color change of Bromcresol Green. Working ranges of 0.5 - 5 mg dm(-3) for Ca, 0.5 - 10 mg dm(-3) for Mg, and 10 - 100 mg HCO3- dm(-3), for alkalinity have been achieved. The results for water samples were comparable to those of the reference methods and to a certified reference water sample. RSDs lower than 5% were obtained, a low reagent consumption and a reduced volume of effluent have been accomplished. The determination rate for calcium and magnesium is 80 h(-1), corresponding to 40 h(-1) per element, while 65 determinations of alkalinity per hour could be carried out.     

EQCM Study of the Couple Thallium(I)/Thallium Amalgam at a Thin Film Mercury Electrode

EQCM and voltammetric data show that thallium(I) ions, which are adsorbed in the region of the positive surface charge, most probably, in the form of the ionic pairs, are not reduced. In this potential region, thallium(I) ions are reduced directly from the solution. At more negative potentials, the previously adsorbed stable ionic pairs slowly undergo transition into the less stable form. From this form, thallium(I) ions can be reduced or desorbed into the solution. The process is best described by a model of one electron, i.e., full charge transfer.     

Radioactive Tracer Study of the Displacement of Iodine Adatoms from Platinized Platinum Electrode by Carbon Monoxide

Radioactive tracer studies confirm the earlier electrochemical results that carbon monoxide can virtually completely displace iodine adatoms. For the first time, it is found that iodine adatoms are not displaced by carbon monoxide when iodide anions are adsorbed in the presence of an upd silver monolayer. The possible reasons for the effect observed are discussed.     

Two-Layered Poly-o-phenylenediamine/Polyaniline Composite: Electrosynthesis and Spectroelectrochemical Properties

Spectroelectrochemical properties of poly-o-phenylenediamine (PPD) and the synthesized composite of PPD and polyaniline—two chemically related polymers containing an amino-substituted benzene ring but having different conduction nature—are studied. The polyaniline synthesis on PPD-modified electrodes involves stages of the reaction initiation, the copolymer formation, and the formation of a polyaniline layer at the copolymer/solution interface.     

Adsorption of Kryptate Complexes of Alkali Metals in Electrolytes of Different Compositions and in the Presence of 1-Adamantanol

Data on the adsorption of kryptates of alkali metals on a mercury electrode are obtained for the first time by a method of the measurement of the differential capacitance as a function of potential and are compared to one another. Shown is that there takes place a deep mutual relationship between the structure of a complex and the regularities of its adsorption. An assumption is put forth about the possibility of adsorption of a free ligand in solutions of lithium kryptate, which possesses relatively low strength. The co-adsorption of sodium kryptate with 1-adamantanol, which forms a two-dimensional condensed layer, is investigated. Established is that the C vs. E curves, obtained in 1 M Na₂SO₄ at a constant activity of 1-adamantanol and a varying concentration of Kryptofix^R 222, exhibit two distinctly pronounced portions, each of which corresponds to predominant adsorption of one of the surface-active components. The region of predominant adsorption of Kryptofix^R 222 expands with its concentration.     

Study of the Surface Tension of the Aqueous Solutions of Dodecylamidoethyldimethylbenzylammonium Chloride

The dynamic and equilibrium surface tensions of aqueous dodecylamidoethyldimethylbenzylammonium chloride solutions of various concentrations at 16, 20, 25, 30, and 35°C are studied for the first time. The effects of the concentration and temperature on the surface tension relaxation are discussed. The possibility of two-dimensional phase transition and its effect on the dynamic behavior of surface tension are considered.     

Determination of Hydroxamic Acids by Thermal-Lens Spectrometry

Conditions are determined for the determination of salicylhydroxamic and acetylhydroxamic acids by thermal-lens spectrometry using iron(III) in an aqueous medium. The detection limits are 6 × 10^–8 and 3 × 10^–8 M, respectively. The sensitivity can be enhanced 3–6 times with the use of aqueous–organic media.