Nanostructured systems based on polymethylsiloxane and nanosilicas with hydrophobic and hydrophilic functionalities

Abstract

Nanostructured adsorbents composed of nanoparticles with hydrophobic and hydrophilic surface functionalities are of interest for practical applications due to the dual nature of their surfaces. To prepare nanostructured hydrogels including a hydrophobic component, its hydrophobicity should be low, e.g., due to the shortest hydrophobic functionalities (–CH3). Therefore, hydrophobic nanosilica (AM1) and polymethylsiloxane (PMS) both with methylsilyl functionalities and residual silanols were selected as components of composites with hydrophilic nanosilica A–300. These hydrophobics were well wetted–stirred with A–300 to control the blend hydrophilicity. To analyze interfacial phenomena in PMS(AM1)/A–300, the temperature behavior of bound water alone or with different co-sorbates and solutes was studied in various dispersion media using low-temperature 1H NMR spectroscopy of static samples. The adsorbents were studied using microscopy, spectroscopy, thermogravimetry, adsorption, and quantum chemistry methods. Obtained results allow us to elucidate several general regularities, caused by the nano-morphology, texture, and structure of components and blends located in different dispersion media, related to the interfacial and temperature behaviors of bound compounds depending on pretreatments changing the organization of ‘soft’ nanostructured systems. This study allows one a deeper insight into the interfacial phenomena in nanostructured hydrophobic/hydrophilic PMS(AM1)/A–300 blends, which could be of interest from a practical point of view for applications as, e.g., drug delivery systems characterized by prolonged release varied for hydrophilic and hydrophobic drugs due to changes in the blend components and their pretreatments.