Encapsulation of three different hydrophobic dyes in functionalized silica particles

This paper describes a method to prepare silica particles able to encapsulate 3 different hydrophobic dyes: Disperse Red, Solvent Red and 2-{4-[4-(Benzyl-ethyl-amino)-phenylazo]-benzenesulfonyl}-ethanol (HESA). Dye doped silica particles were prepared by the sol–gel process in aqueous medium, with a base catalyst, using various concentrations of a “home made” surfactant (named NP₉-Si). The surfactant is the addition byproduct of –OH groups of polyethylene glycol nonylphenyl ether Tergitol^® NP-9 with -NCO groups from (3-isocyanatopropyl) triethoxysilane and was added to increase both the stabilization of the silica particles and the compatibility of the inorganic network versus the dopant (the aromatic dye). It was shown that there is an optimum range of the amount of surfactant which should be added in the sol–gel reaction system. If a higher amount of surfactant is used, it forms probably micelles which entrap the dye and prevent its encapsulation in the formed silica particles. Because the silica particles are designed to encapsulate systems containing aromatic derivatives (aromatic dyes) we used phenyltriethoxy silane and tetraethylorthosilicate as silica precursors. As coupling agent for the silica network we used a bis (trialkoxysilane) derivative—1,2-bis (triethoxy silyl) ethane.     

Superparamagnetic magnetite–divinylbenzene–maleic anhydride copolymer nanocomposites obtained by dispersion polymerization

Magnetite alternating copolymers divinylbenzene–maleic anhydride (DVB–MA) composites were prepared by dispersion polymerization. Because magnetite is used as a complex with oleic acid (Fe₃O₄OLA), the final hybrids show good dispersion of inorganic nanofillers in the polymer matrix. The obtained composites were analyzed by infrared absorption spectrometry, diffuse reflectance in visible light, thermogravimetry, X-ray fluorescence, X-ray diffraction, dynamic light scattering, scanning electron microscopy and vibrating sample magnetometry. The obtained results indicate the successful preparation of magnetite nanoparticles with an average size of about 23 nm dispersed in micrometer size copolymer spherical particles, which relative content can be controlled via the processing parameters. A relationship between the relative content of magnetite nanoparticles and the size of the polymer particles, with direct influence on the diffuse reflectance in the visible domain, was observed. A superparamagnetic behavior was evidenced at room temperature with a blocking temperature lower than as expected from the bulk anisotropy constant and the average size of the magnetite nanoparticles. Both the unexpected low blocking temperature and the observed low specific magnetizations were explained by a defected and poor crystalline structure of the magnetite nanoparticles, giving rise to spin disorder and diminished crystalline anisotropy constant.     

Recycled polypropylene with improved thermal stability and melt processability

Journal of Thermal Analysis and Calorimetry - Polypropylene (PP) is a versatile polymer, with a wide range of applications, from household appliances to packaging and automotive components....