Hybrid RF-Si Xerogels: A Cost-Effective Proposal for Insulator Materials

Hybrid xerogels RF/Si were synthesized by controlling the chemical variables involved in the polymerization process (i.e., molar ratios, dilution ratio, catalysts, etc.) and evaluated as insulator materials. Higher insulating performances were recorded for these hybrids compared with their counterparts made from only one of their components (i.e., RF or Si xerogels with similar porous characteristics). The analysis of chemical and structural features correlated with heat transfer methods was useful in understanding the sum of contributions involved in the thermal conductivity of RF/Si xerogels. Variables such as roughness and tortuosity can be used to improve the performance of xerogels from a different perspective. In this way, thermal conductivities of 25 mW/mK were achieved without lengthy process steps or special drying methods. Knowledge of material design and the use of microwave heating during the synthesis allowed us to approach a simple and cost-effective process. These results suggest that the hybrid materials developed in this work are a good starting point for the future of the massive production of insulation materials.

Hybrid Xerogels: Study of the Sol-Gel Process and Local Structure by Vibrational Spectroscopy

The properties of hybrid silica xerogels obtained by the sol-gel method are highly dependent on the precursor and the synthesis conditions. This study examines the influence of organic substituents of the precursor on the sol-gel process and determines the structure of the final materials in xerogels containing tetraethyl orthosilicate (TEOS) and alkyltriethoxysilane or chloroalkyltriethoxysilane at different molar percentages (RTEOS and ClRTEOS, R = methyl [M], ethyl [E], or propyl [P]). The intermolecular forces exerted by the organic moiety and the chlorine atom of the precursors were elucidated by comparing the sol-gel process between alkyl and chloroalkyl series. The microstructure of the resulting xerogels was explored in a structural theoretical study using Fourier transformed infrared spectroscopy and deconvolution methods, revealing the distribution of (SiO)4 and (SiO)6 rings in the silicon matrix of the hybrid xerogels. The results demonstrate that the alkyl chain and the chlorine atom of the precursor in these materials determines their inductive and steric effects on the sol-gel process and, therefore, their gelation times. Furthermore, the distribution of (SiO)4 and (SiO)6 rings was found to be consistent with the data from the X-Ray diffraction spectra, which confirm that the local periodicity associated with four-fold rings increases with higher percentage of precursor. Both the sol-gel process and the ordered domains formed determine the final structure of these hybrid materials and, therefore, their properties and potential applications.

Synthesis and Study of Lidocaine Hydrochloride from Polymeric Film as a Wound Dressing

Introduction: Among various carrier materials capable of drug controlled-release, silica xerogels have been found to be noteworthy for loading and sustaining drug release. These silica xerogels were synthesized through sol-gel technology using Tetraethylortosilicate (TEOS) as a silica precursor. Methods: This study was an experimental basic research, which aimed to characterize the effect of adding chitosan to silica xerogels on Morphology, surface area and topography as well as mechanical behavior of the hybrid films. Furthermore, the lidocaine hydrochloride was incorporated on to the hybrid chitosan-silica xerogels and drug release behavior of the hybrid xerogels was evaluated and compared with pure silica xerogels. In addition, the covalent bond between chitosan chains and silica network was verified by FTIR; MTT assay was performed to evaluate cytotoxicity of the final system. Results: The release profile of hybrid xerogels showed biphasic mode of release and approximately 71 % accumulative release rate. Chitosan slightly decreased burst effect and release rate, but extended release period in comparison with silica xerogel. Moreover, blending of chitosan and TEOS enhanced tensile elongation and reduced the average pore size of TEOS-based xerogels. Conclusion: In conclusion, this in vitro study showed that the sol–gel method is useful for entrapping lidocaine hydrochloride in the pores of xerogels and its controlled release. Likewise, blending of chitosan and TEOS improves tensile mechanical properties of resulted biocompatible films. Hence, the final organic-inorganic films are capable to be applied as a coating or thin films in biomedical applications.

Porous organic–inorganic hybrid xerogels for stearic acid shape-stabilized phase change materials

The high surface area, porosity and gel properties of MOG-100 (Cr) ensure the excellent thermal properties of SA@MOG-100 (Cr) composites.