Surface modification of inorganic nanoparticles for development of organic–inorganic nanocomposites—A review

Nanoparticles and nanocomposites are used in a wide range of applications in various fields, such as medicine, textiles, cosmetics, agriculture, optics, food packaging, optoelectronic devices, semiconductor devices, aerospace, construction and catalysis. Nanoparticles can be incorporated into polymeric nanocomposites. Polymeric nanocomposites consisting of inorganic nanoparticles and organic polymers represent a new class of materials that exhibit improved performance compared to their microparticle counterparts. It is therefore expected that they will advance the field of engineering applications. Incorporation of inorganic nanoparticles into a polymer matrix can significantly affect the properties of the matrix. The resulting composite might exhibit improved thermal, mechanical, rheological, electrical, catalytic, fire retardancy and optical properties. The properties of polymer composites depend on the type of nanoparticles that are incorporated, their size and shape,their concentration and their interactions with the polymer matrix. The main problem with polymer nanocomposites is the prevention of particle aggregation. It is difficult to produce monodispersed nanoparticles in a polymer matrix because nanoparticles agglomerate due to their specific surface area and volume effects. This problem can be overcome by modification of the surface of the inorganic particles. The modification improves the interfacial interactions between the inorganic particles and the polymer matrix. There are two ways to modify the surface of inorganic particles. The first is accomplished through surface absorption or reaction with small molecules, such as silane coupling agents, and the second method is based on grafting polymeric molecules through covalent bonding to the hydroxyl groups existing on the particles. The advantage of the second procedure over the first lies in the fact that the polymer-grafted particles can be designed with the desired properties through a proper selection of the species of the grafting monomers and the choice of grafting conditions

Nanofibrillated cellulose: surface modification and potential applications

Interest in nanofibrillated cellulose has been increasing exponentially because of its relatively ease of preparation in high yield, high specific surface area, high strength and stiffness, low weight and biodegradability etc. This biobased nanomaterial has been used mainly in nanocomposites due to its outstanding reinforcing potential. Solvent casting, melt mixing, in situ polymerization and electrospinning are important techniques for the fabrication of nanofibrillated cellulose-based nanocomposites. Due to hydrophilic character along with inherent tendency to form strong network held through hydrogen-bonding, nanofibrillated cellulose cannot uniformly be dispersed in most non-polar polymer matrices. Therefore, surface modification based on polymer grafting, coupling agents, acetylation and cationic modification was used in order to improve compatibility and homogeneous dispersion within polymer matrices. Nanofibrillated cellulose opens the way towards intense and promising research with expanding area of potential applications, including nanocomposite materials, paper and paperboard additive, biomedical applications and as adsorbent