Role of solvation forces in the gelation of fumed silica–alcohol suspensions

2006 ◽  
Vol 304 (2) ◽  
pp. 348-358 ◽  
Author(s):  
William E. Smith ◽  
Charles F. Zukoski
Keyword(s):  
Fumed Silica ◽  
Solvation Forces

Modification of DABA/BMI Composites by Silane Compound and Fumed SiO2

2012 ◽  
Vol 622-623 ◽  
pp. 1006-1013
Author(s):  
Nazakat Alia ◽  
Qiu Yu Zhang ◽  
Yin Wu ◽  
Ying Chen
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Scanning Electron Microscopy ◽  
Thermal Properties ◽  
Fumed Silica ◽  
Heat Stability ◽  
Nano Composite ◽  
Bending Modulus ◽  
Scanning Electron

In this present investigation, at first, Dially bisphenol A (DABA)/Bismaleimide (BMI) system was modified with gamma-aminopropyltriethoxy silane (KH550). The objective of the work was to study the effect of addition of various weight percentages of KH550 into BMI/DABA composites on its mechanical properties, thermal properties and morphorogy. Further modification was carried out with fumed silica. The role of KH550 was discussed in these composites prepared. Nancomposites were characterized by differential DSC, TGA, and scanning electron microscopy SEM. TGA results confirmed that the heat stability of the nano composite DABA/BMI/KH550 is improved compared with DABA/BMI system. SEM results indicated that the fumed silica dispersed homogeneously in DABA/BMI/KH550 matrix on nanoscale. Mechanical results shows that newly developed system has improved bending modulus to 4.0GPa, while with incorporation of fumed SiO2 impacted strength also improved to 20.60kJ/m2.

Role of Colloidal Silicon Dioxide in Eudragit In-Situ Forming Gel

2012 ◽  
Vol 581-582 ◽  
pp. 146-149
Author(s):  
Jongjan Mahadlek ◽  
Thawatchai Phaechamud
Keyword(s):  
Silicon Dioxide ◽  
Physical Properties ◽  
Fumed Silica ◽  
Newtonian Flow ◽  
Gelling Agents ◽  
Dispersing Medium ◽  
Methyl Pyrrolidone ◽  
Thickening Agents

Colloidal silicon dioxide (Aerosil) is fumed silica that has been used as gelling agents, thickening agents and filling agents. The objectives of this study were to characterize the effect of hydrophilic (aerosil 200) and hydrophobic (aerosil R972) colloidal silicon dioxide on physical properties of eudragit gels which N-methyl-pyrrolidone was employed as dispersing medium. The samples were investigated in terms of viscosity, rheology and syringeability. The results indicated that the aerosil 200 and aerosil R972 amount influenced the viscosity, rheology and syringeability of the prepared gels. Viscosity and syringeability of the systems were increased with an increased amount of both aerosils. However, the viscosity and syringeability of the prepared gels containing aerosil 200 were increased higher than that of systems containing aerosil R972. The rheological behaviors of all systems consisting aerosil 200 and R972 were non-Newtonian flow. These studies demonstrated that aerosil 200 and R972 could improve the physical properties of eudragit gels dispersed in N-methyl-pyrrolidone.

scholarly journals Understanding the Role of Solvation Forces on the Preferential Attachment of Nanoparticles in Liquid

ACS Nano ◽  
2015 ◽  
Vol 10 (1) ◽  
pp. 181-187 ◽  
Author(s):  
David A. Welch ◽  
Taylor J. Woehl ◽  
Chiwoo Park ◽  
Roland Faller ◽  
James E. Evans ◽  
...  
Keyword(s):  
Preferential Attachment ◽  
Solvation Forces

scholarly journals Nucleotide Interaction with Chitosan Layer Deposited on Fumed Silica Surface: Practice and Theory towards Establishing the Mechanism at the Molecular Level

2020 ◽  
Author(s):  
Tetyana Budnyak ◽  
Nataliya Vlasova ◽  
Lyudmila P. Golovkova ◽  
Olga Markitan ◽  
Glib V. Baryshnikov ◽  
...  
Keyword(s):  
Fumed Silica ◽  
Electrostatic Interactions ◽  
Silica Surface ◽  
Gene Transfection ◽  
Decisive Role ◽  
Formation Constants ◽  
Surface Complex ◽  
Complex Formation Constants ◽  
Efficient Gene

The growing interest in gene therapy is coupled to the strong need for the development of safe and efficient gene transfection vectors. A composite based on chitosan and fumed silica has been found to be a prospective gene delivery carrier. This study presents an investigation of the nature of the bonds between a series of mono-, di- and triphosphate nucleotides with a chitosan layer deposited on a fumed silica surface. It was observed that the adsorption of most of the studied nucleotides is determined by the formation of one surface complex. Experimentally measured surface complex formation constants (logK) of the nucleotides were found to be in range 2.69–4.02 which is higher than that for the orthophosphate (2.39). Theoretically calculated nucleotide complexation energies for chitosan deposited on the surface range from 11.5 to 23.0 kcal·mol<sup>–1</sup> in agreement with experimental data. The adsorption of nucleotides was interpreted using their calculated speciation in aqueous solution. Based on the structures of all optimized complexes determined from quantum-chemical PM6 calculations, electrostatic interactions between the surface-located NH<sub>3</sub><sup>+</sup> groups and –PO<sub>3</sub>H<sup>–</sup>–/–PO<sub>3</sub><sup>2-</sup> fragments of the nucleotides was identified to play the decisive role in the adsorption mechanism. The saccharide fragment of monophosphates also plays an important role in the binding of the nucleotides to chitosan through the creation of hydrogen bonds; in the case of di- and triphosphates the role of the saccharide fragment decreases significantly.

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