Nanocomposites of polymers and inorganic particles: Preparation, structure and properties

Abstract

Although composites with, e.g.nanosized SiO2, TiO2, carbon black or gold are known for a long time, an increasing number of polymer composites comprising inorganic nanoparticles have been described only in the last 15 years. Frequently employed inorganic materials include metals (e.g. gold, silver or copper), semiconductors (e.g. PbS or CdS) or clay minerals (e.g.montmorillonite or vermiculite). In most cases, nanocomposites with spheric or plate like particles have been prepared so far but materials with nanorods (rod like particles, including nanotubes) also attracted attention. The structure of nanocomposites is essentially established by the arrangement of the particles in the polymer matrix. The particles may be dispersed as individual primary particles or as agglomerated particles (secondary particles), and the primary or secondary particles can be arranged randomly or in an ordered or oriented state, depending on the method of nanocomposite preparation and processing (including, e.g. coprecipitation, coevaporation, spin coating or drawing). In order to avoid agglomeration, the nanoparticles are frequently synthesised in situ or applied as surface modified particles, where a spheric inorganic core is preferentially surrounded by a shell composed of organic molecules (core–shell particles). Surface modification is applied routinely for clays, which is of importance for the degree of delamination of the individual silicate layers in the matrix (intercalation or exfoliation). Materials properties of nanocomposites, such as optical transparency, colour (including dichroism), iridescence, catalytic activity or superparamagnetism, can be favourable when compared with analogous composites with larger particles, and these properties may also be influenced by the structure of nanocomposites. The properties of nanocomposites are considered to provide applications in the areas of, e.g. optics, catalysis, electronics, magnetism or mechanics.

Silver nanoparticle deposition on hydrophilic multilayer film surface and its effect on antimicrobial activity

“…However, the fine dispersion of nanoparticles in a polymer using conventional compounding techniques is a very difficult task, due to the strong tendency of nanoparticles to agglomerate and aggregate, losing the benefits of the nanometric size. 14,15 The polymer-nanoparticle interface plays an important role. Thus, the polymer modification with alkoxysilane groups has been applied in some studies to provide the covalent bonding to inorganic nanomaterials.…”

Highly Concentrated Colloidal Dispersion of Decanoic Acid Self-assembled Monolayer-protected CeO2 Nanoparticles Dispersed to a Concentration of up to 77 wt % in an Organic Solvent

“…Actually, surface modifications of NPs by organic modifiers have succeeded in dispersing NPs and have been recognized as a common technique. 1,2 However, when one thinks about perfect dispersion (dispersion without any flocculation, agglomeration, and aggregation) at very high NP content and stable dispersion in polymers, the overall design of NPcontaining composite (hybrid material) is still an important issue. In the case of dispersion in nonpolar solvents, repulsive force between NPs (different from electrostatic force) should be considered because of the small dielectric constant of solvents and small radius of NPs; i.e., electrostatic repulsive force between NPs is very small and less important in nonpolar solvents.…”

“…In addition, the packing density of decanoic acid in the SAM was calculated from the weight loss of the TG ( Figure 5) and the average size of the decanoic acid SAM-protected CeO 2 NPs, and graft density was calculated to be 4.97 chains/nm 2 . The density was almost the maximum packing density of fatty acid SAMs, i.e., 2 , which was calculated from the crystalline density of fatty acids. 13 Combining this with the calculated graft density of the CeO 2 NPs, we concluded the SAM on the CeO 2 NPs was in the quasi-crystalline state.…”

Evaluation of a new processing method for improved nanocomposite dispersions

“…The unfavorable interaction energy between the nanoparticle and polymer-matrix provides a driving force for nanoparticle agglomeration during melt processing. 16,22,32 Several research groups have proposed chemical and/or physical techniques to improve the nanoparticle dispersion in PNCs. Chemical techniques are intended to optimize the polymer-matrix interaction energy.…”