Hydrophobic grade fumed silicas are generally used in tabletting as lubricants. They are also found to retard the release of pharmaceutical actives. This is because of their hydrophobic nature, which gives good cohesive and adhesive properties. considering this point it was thought that they could be used as dry coating agents for solid dosages forms. The model drug selected for this work was p...

Hydrophobic grade fumed silicas are generally used in tabletting as lubricants. They are also found to retard the release of pharmaceutical actives. This is because of their hydrophobic nature, which gives good cohesive and adhesive properties. considering this point it was thought that they could be used as dry coating agents for solid dosages forms. The model drug selected for this work was p...

hydrophobic grade fumed silicas are generally used in tabletting as lubricants. they are also found to retard the release of pharmaceutical actives. this is because of their hydrophobic nature, which gives good cohesive and adhesive properties. considering this point it was thought that they could be used as dry coating agents for solid dosages forms. the model drug selected for this work was p...

High-resolution ac calorimetry has been carried out on dispersions of aerosils in the liquid crystal octyloxycyanobiphenyl (8OCB) as a function of aerosil concentration and temperature spanning the crystal to isotropic phases. The liquid crystal 8OCB is elastically stiffer than the previously well studied octylcyanobiphenyl (8CB)+aerosil system and so general quenched random-disorder effects an...

High-resolution ac calorimetry has been used to study the nematic to smectic- A (N-SmA) phase transition in the liquid crystal octylcyanobiphenyl (8CB) confined in aligned colloidal aerosil gels. A stable and robust nematic alignment was achieved by repeated thermal cycling of the samples in the presence of a strong uniform magnetic field. In some ways (such as transition temperature and integr...

The object of research is the hydrophobization a coating based on styrene-acrylic copolymer and cellulose acetate butyrate with pyrogenic silicon dioxide. hydrophobicity or hydrophilicity surface depends mainly chemical structure its roughness. A relief hydrophilic will be wetted much more easily than flat same material, vice versa – an increase in roughness hydrophobe accompanied by pronounced...

We report on a comparison between the random disorder effects of an hydrophobic (R812) or an hydrophilic (A380) aerosil on the order and dynamics of the 3βDOXYL-5α-cholestane spin probe in the liquid crystal 4-n-pentyl-4’-cyanobiphenyl (5CB) using the ESR technique. Increasing the aerosil concentration up to 3 wt % the probe order parameter is depressed with a larger effect for the hydrophilic ...

This study explores the role of aerosil dispersion on activated phase transitions of bulk octylcyanobiphenyl (8CB) liquid crystals by performing heating rate-dependent experiments. Differential scanning calorimetry (DSC) was used at various heating ramp rates in order to probe the activated phase dynamics of the system. The system, LC1-xSilx, was prepared by mixing aerosil nanoparticles (7 nm i...

A high-resolution calorimetric spectroscopy study has been performed on pure glycerol and colloidal dispersions of an aerosil gel in glycerol covering a wide range of temperatures from 300 to 380 K, deep in the liquid phase of glycerol. The colloidal glycerol+aerosil samples with 0.07, 0.14, and 0.32 g of silica per cm3 of glycerol reveal activated energy (thermal) dynamics at temperatures well...

We have studied a system composed of an hydrophobic aerosil (R812) dispersed in the liquid crystal 4-n-octyl-4’-cyanobiphenyl (8CB) using the spin probe ESR technique and, in particular, we have determined, for different aerosil concentrations, the temperature dependence of the orientational order parameter 〈P2〉 and the rotational diffusion coefficient D⊥ of the probe 5-doxyl stearic acid in th...