The state of water in swollen polymers

It is shown that by low frequency measurements in hydrophilic polymers only one state of water is observed. Water behave as a classical plasticizer and ice melting in polymer is similar to ice melting in binary simple mixture. The non crystallizable water in these systems is explained by the Tg regulation effect. In oriented swollen polymers, only one state of water is observed in the time scale ∼ 1/ω_q = 10⁻⁵ s by deuterium NMR. This technique gives information on the mean orientation of D₂O molecules in the oriented polymer and on the fraction of mobile water molecules. The concept of bound and unbound water is not relevant for explaining the DSC and D-NMR results.     

Heavy fermion superconductivity

The quest for a precise identification of the symmetry of the order parameter in heavy fermion systems has really started with the discovery of the complex superconducting phase diagram in UPt₃. About 10 years latter, despite numerous experiments and theoretical efforts, this is still not achieved, and we will quickly review the present status of knowledge and the main open question. Actually, the more forsaken issue of the nature of the pairing mechanism has been recently tackled by different groups with macroscopic or microscopic measurement, and significant progress have been obtained. We will discuss the results emerging from these recent studies which all support non-phonon-mediated mechanisms.     

Cryptanalysis of the Matsumoto and Imai Public Key Scheme of Eurocrypt'98

In 1 Matsumoto and Imai developed a new public key scheme, called C*, for enciphering or signing. (This scheme is completely different from and should not be mistaken with another scheme of Matsumoto and Imai developed in 1983 in 7 and broken in 1984 in 8). No attacks have been published as yet for this scheme. However, in this paper, we will see that—for almost all keys—almost every cleartext can be found from its ciphertext after only approximately m ² n ⁴ log n computations, where m is the degree of the chosen field K and mn is the number of bits of text. Moreover, for absolutely all keys that give a practical size for the messages, it will be possible to find almost all cleartexts from the corresponding ciphertexts after a feasible computation. Thus the algorithm of 1 is insecure.     

Silica-modified electrode for the selective detection of mercury

Pure silica particles were dispersed within carbon paste and the resulting modified electrode was applied to the selective voltammetric detection of mercury(II) species after their accumulation at open circuit. The remarkable selectivity observed between pH 4 and 7 was attributed to the intrinsic adsorption mechanism which involves a condensation reaction between mercury(II) hydroxide and hydroxyl groups on the silica surface, leading to the formation of an inner-sphere-type surface complex. After optimization with respect to the electrode composition, the detection medium, and the voltammetric scan mode, a linear response was obtained in the concentration range between 2 × 10⁻⁷ M to 1 × 10⁻⁵ M, by applying anodic stripping square wave voltammetry. Various silica samples were used and their sorption behavior was discussed in relation to their specific surface area and porosity. The effect of chloride and pH on the accumulation of mercury(II) on silica was also investigated. Received: 4 September 1999 / Accepted: 5 January 2000     

Novel calix[4]cryptands: “Mappemonde II” and “Mill II”

Two novel calix[4]cryptands were synthesized from 1,3‐alternate calix[4]bis‐azacrown. “Mappemonde II” consists of one 1,3‐calix[4]bis‐azacrown wrapped by a benzo‐crown ether loop. “Mill II” is composed of two 1,3‐calix[4]bis‐azacrowns linked by two benzo‐crown ether strands.     

Indium tellurium trioxide chloride,InTeO3Cl

The new oxy­chloride InTeO₃Cl was synthesized from a mixture of In₂O₃, InCl₃ and TeO₂. Its structure has been determined from single‐crystal X‐ray diffraction data. The structure is composed of layers separated by a van der Waals gap. The layers consist of edge‐sharing chains of [InO₄Cl₂] octahedra linked through [TeO₃] trigonal pyramids. No free Cl atoms are located between the layers.     

p‐Methyl­tetrahomodioxacalix­[4]­arene

The title compound, 7,13,21,27‐tetramethyl‐3,17‐dioxapenta­cyclo­[23.3.1.1^5,9.1^11,15.1^9,23]ditriaconta‐1(29),5,7,­9(30),­11(31),‐12,­14,19(32),20,22,25,27‐dodecaene‐29,30,31,32‐tetraol, C₃₄H₃₆O₆, assumes in the solid state a very distorted cone‐like conformation stabilized by intramolecular simple and bifurcated hydrogen bonds involving both phenolic and ether O atoms. One part of the mol­ecule, comprising an ether link, is included in the cavity of an adjacent calixarene related by a screw axis, giving rise to a one‐dimensional self‐inclusion polymer.     

On the interaction mechanism of radical photoinitiators with monomers

Rate constants of quenching of triplet excited ketones by several monomers were determined through time‐resolved laser spectroscopy or culled from the literature. The semi‐empirical calculation method PM3 allows the quenching mechanisms to be refined and can be used to predict the reactivity of aromatic ketones toward monomers. It is apparent from both experimental results and theoretical calculations that the rate constant (k_q ) measured for the bimolecular quenching between the triplet state of a given aromatic ketone and both electron‐rich as well as electron‐poor monomers, depends linearly on the free enthalpy of formation of the regioselectively favored 1,4‐biradical, which is the primary reaction step of the ketone/monomer interaction. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1785–1794, 2000