These properties are determined by a type of organosilicon polymer/silica interaction, a thickness and architecture of the grafted surface layer. The most promising among the above materials are polyorganosiloxane-modified pyrogenic silicas which are characterized by thermal stability, chemical inertness, and hydrophobic properties. The hydrophobic nanodispersed silicas are widely used as fillers for adhesives and sealants, epoxy resins, vinylester resins, gelcoats, cable gels, and natural and artificial oils and grease, as well as component of biological dispersions and sorbents. The characteristics of surface structure were interpreted in terms of density of polymer-silica bonds at the interfaces that, usually, are reduced for modified surfaces, in a coupling with conformation model that accented the shape of chains (arch- and console-like) adsorbed on solid surfaces. Results suggest that the highest hydrophobicity (contact angle θ = 135°–140°) is achieved in the case when silica modified with the PMPS/DMC mixture using multistage approach that providing a formation of the monomolecular layer of polysiloxane at the first modification step. Modification with a similar composition of the PMPS/DMC mixture, even with different polymer amount at each stage, provides the worst hydrophobicity. The results indicate a significant effect of the PMPS/DMC ratio at each modification stage on hydrophobic properties of modified silicas. Coating microstructure, morphology, and hydrophilic-hydrophobic properties of nanoparticles were estimated. Samples were characterized using FTIR spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM), and elemental analysis (CHN analysis). Powders of nanodispersed silica with chemisorbed polymethylphenylsiloxane (PMPS) were synthesized by solvent-free chemical assembly technique with a dimethyl carbonate (DMC) as scission agent. The method of a chemical assembly of the surface polymeric layer with high contents of the modifying agent was developed.
0 kommentar(er)
