Supramolecular Silicone Elastomers with Healable and Hydrophobic Properties Crosslinked by “Salt‐Forming Vulcanization”

In this article, supramolecular silicone elastomers with self‐healing function were first prepared by simple and controllable “salt‐forming vulcanization” of polyaminopropylmethylsiloxane with acids. Their structures and micrographs were verified by Fourier transform infrared spectra, Small‐angle X‐ray scattering experiments and atomic force microscope. The experimental results showed that the ion‐association complexes were formed during vulcanization, and the obtained elastomers displayed self‐healing and good mechanical properties even if the cross‐linking agent was excessed. The thermogravimetric analysis showed that the elastomers crosslinked by inorganic acid were stable under high temperature. Unexpectedly, bionic structures were observed in the elastomers, which further changed the hydrophobicity of the surfaces of the elastomers physically. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 903–911     

Effects of controllable process factors on Al rear surface bumps in Si solar cells

High efficiency solar cells require good back surface field passivation and high back reflectance in the rear Al region. In module processes, wafer-based solar cell can break through stress during soldering uneven rear aluminum surfaces - a serious problem that affects throughput. This work examined rear surfaces with respect to controllable process factors such as ramping and cooling rates during rapid thermal processing, and the fineness of aluminum powder used in the screen-printed paste. A faster ramp up rate resulted in a uniform temperature gradient between the aluminum and silicon surfaces. As a results, the bumps on the aluminum surface were small and of high density. Fine aluminum metal powder in the paste for screen-printing contact points resulted in large distribution, high density bumps. Bumps formed during cooling in metallization, their sizes and densities were dependent the on uniformity of the aluminum and silicon liquid wetting of the silicon surface.     

Proton transfer rate‐equilibria in apolar aprotic solvents: a historical perspective

Low dielectric constant apolar aprotic solvents, although employed on a limited scale for studying proton transfer reactions as compared with commonly used polar protic or dipolar aprotic ones, offer some particular advantages, namely, specific solute–solvent interactions are virtually eliminated and proton transfer occurs directly in an apolar aprotic solvent. An intriguing feature of these reactions is their general acid‐catalyzed/base‐catalyzed kinetics with a time scale over microseconds to minutes. In fact, the true or intrinsic relative strengths of acids/bases when measured in such solvents come to the fore much more clearly than those obtained in other classes of solvents. Recently, a review documenting the post‐1980 developments relating to proton transfer reactions in apolar aprotic solvents has been published. The present article is a commentary of the pre‐1980 developments in this area since the 1920s Brønsted–Lowry's “proton cult” of acid–base theory. Copyright © 2016 John Wiley & Sons, Ltd.     

Entropy and equilibrium property of QCD-instanton induced final state in deep-inelastic scattering

The scaling and additivity properties of Rényi entropy in rapidity space of the instanton final state (IFS) and current jet identified by the r-sorting method from the QCDINS Monte Carlo event sample are to saturation with decreasing phase space scale. Furthermore, it is found that the additivity of H2 holds well for the IFS in narrow rapidity windows at different positions. These results indicate that the IFS produced in the instanton-induced process of deep inelastic scattering has reached local equilibrium.     

Nonlinear optical characterization of cluster dynamic in water in oil microemulsion by a pump probe laser beam technique

We present a new pump probe laser beams configuration for the nonlinear optical characterization of microemulsions. We detect the variation of the on-axis optical intensity of the probe beam as generated by the concentration profile induced in an optically thin film of microemulsion by the pump beam. A mathematical model has been introduced to describe the phenomenon. The technique allows the determination of both Kerr-like optical nonlinearity and time constants and, therefore, it gives information both on cluster dimension and their shape. We discuss its application to WAD (water/AOT/decane, where AOT denotes sodium-bis-di-ethyl-sulfosuccinate) with the application of a strong electric field of optical source. Comparison between theoretical predictions and experimental results confirms the presence of giant optical nonlinearity in the absence of turbidity divergence. Chainlike shape of clusters, of the kind already reported with the application of strong electric field, could justify this result. Received 26 October 2002 RID="a" ID="a"e-mail: vicari@na.infn.it     

The behaviour of cellulose in hydrated melts of the composition LiXċn H2O (X=I−, NO3−, CH3COO−, ClO4−)

The dissolution behaviour of cellulose in low temperature molten salts was investigated. Depending on the chosen anions in the melt, cellulose shows different reaction behaviour in different Li⁺containing melts. Dissolution of the polymer was observed in molten LiClO₄3H₂O and molten LiI2H₂O. In the hydrated melts of LiCH₃COO2H₂O and LiNO₃3H₂O a fine distribution of cellulose was stated. Cellulose can be regenerated by cooling the melt and removing the salt by dissolution in water.The structure of the recrystallized product is determined by the used low temperature molten salt.     

Bulk and microscopic properties of copolymer networks in mixed aqueous solvents

Amphiphilic films and hydrogels have been prepared from ethanol/water solutions containing a hydrocarbon-grafted water-soluble cellulose ether. These materials are characterized by dispersed hydrophobic microdomains which form spontaneously in the solvent due to the inherent incompatibility of the side chains with water. At low applied shear stress, the microdomains behave as temporary linkages of finite lifetimes, imparting viscoelastic properties to the networks. The molecular weight between microdomains was found to be independent of the volume fraction of polymer in the gel, and the number of linkages per backbone ranges from 22.8 ± 1.3 to 26.2 ± 1.5 over the frequency range 30–50 rad/s. The behavior of the solutions and gels was characterized using fluorescence and dynamic rheological measurements. It was demonstrated that the microdomains are capable of sequestering water-insoluble solutes. © 1992 John Wiley & Sons, Inc.     

Chelation of Na+ cations in nonaqueous solvents. Structural requirements and methodological considerations

Intrinsic formation constants for complexes of Na⁺ ions with a series of polyamines have been determined from²³Na NMR measurements in binary mixtures of tetrahydrofuran (THF) and amines. The results show in a totally unambiguous manner a regular decrease in the magnitude of the chelate effect with the number of atoms intervening between the nitrogen ligators. The key assumption, tetracoordination of the cation, is critically examined, and experimental evidence is adduced in its support.