Siloxane-based nanobuilding blocks by reaction between silanediol and trifunctional silicon alkoxides

The preparation of nanostructured organic-inorganic materials by assembling of nanobuilding blocks allows controlling the extent of phase interaction, which in its turn governs structure-properties relationships. We present here the synthesis of siloxane-based nanobuilding blocks prepared by reacting diphenylsilanediol with vinyltriethoxysilane and triethoxysilane. The reaction products were obtained by non-hydrolytic condensation between silanediol and ethoxide groups in inert atmosphere, in the presence of pyridine, triethylamine or butyl lithium. Different synthetic conditions were examined by means of ATR-FTIR and NMR spectroscopies, showing the formation of siloxane bonds. In the case of triethoxysilane the reaction carried out in the presence of pyridine leads to Si-H bond preservation in the final product. Air stable products with improved Si-O-Si hydrolytic stability can be obtained by removal of the base after the reaction completion. The condensation products can be described as a mixture of siloxane rings involving difunctional and trifunctional silicon units. © 2004 Kluwer Academic Publishers

Preface

This Special Issue is dedicated to the memory of Klaus Muller. This Special Issue focuses on Sol–Gel R&D in Italy, with the purpose of giving a short overview of current research trends in this field and presenting the main laboratories working on sol–gel. The Italian community, though it has a small number of researchers, has been one of the most active in sol–gel research from the very beginning. The first International Sol–Gel Workshop of the series was held in Padova, with several laboratories playing a pivotal role in basic sol–gel research, which has been widely recognized worldwide. This Issue also has the purpose of increasing international collaborations along with information on those who work in this field, and hopefully should be the first of a series of Special Issues dedicated to different countries. We would like to thank all the contributors to this special Issue and in particular to the Editor-in-Chief of the Journal of Sol–Gel Science and Technology, Michel Aegerter, for his precious support. We have dedicated this Special Issue to Prof. Klaus Muller from the University of Trento who suddenly passed away during the preparation of the Issue; it is an enormous loss for our community and his family. The Special Issue Editors Plinio Innocenzi, Giovanna Brusatin, Antonio Aronne, Sandra Dire`, Franca Morazzon

Effects of Graphene-Based Fillers on Cathodic Delamination and Abrasion Resistance of Cataphoretic Organic Coatings

This study aims to demonstrate the excellent protective performance of functionalized graphene oxide (fGO) flakes in acrylic cataphoretic coatings. The filler content provides an important contribution in improving the chemical and mechanical resistance of the acrylic matrix. The morphology of the fillers was first investigated by optical and electron microscopy, analysing the distribution of the fGO flakes within the polymer matrix. After that, the flakes were added to the cataphoretic bath in different concentrations, resulting in four series of samples. The cathodic delamination of the coatings was assessed with cathodic polarization cycles and with measurements carried out with a scanning Kelvin probe. Finally, the abrasion resistance at the macroscopic and microscopic level was studied by scrub testing and scratching atomic force microscopy analysis, respectively. The incorporation of fGO at the optimized concentration of 0.2 wt.% greatly increases the cathodic delamination resistance of the acrylic matrix, resulting in an effective barrier against the effects of absorbed aggressive substances. Graphene-based fillers also enhance abrasion resistance, thanks to their high mechanical strength. Thus, this work demonstrates the great protective benefits that can be obtained when using fGO flakes as reinforcing fillers in cataphoretic coatings

Optimisation and memristive response of sol-gel derived TiO2 thin films

Herein, we developed a series of Pt/TiO2/Pt/Ti/SiO2 resistive switching materials with a variation in chemical composition of TiO2 in an attempt to evaluate the parameters affecting the memristive switching behavior and, therefore, to optimize and control it. Different chemical compositions of TiO2 were obtained by annealing the films at 400 °C for 1 hour in diverse atmospheric conditions, such as air, vacuum and oxygen environments. The elemental composition of the produced samples was analyzed by X-ray photoelectron spectroscopy (XPS), revealing the different stoichiometric ratio of Ti/O and doping/contamination with silicon, carbon, and nitrogen depending on the annealing conditions. The preliminary I-V curves were acquired with Pt dish or wire, serving as a top electrode. The results showed a superior stability, durability and reproducibility of the resistive switch behavior observed in the samples containing oxidized silicon impurities. In addition to the electrical studies, the evolution of Pt dish top electrode was monitored by optical microscopy and scanning electron microscopy (SEM), revealing mechanical and electrochemical damage of the electrode during the electroforming step