Polymer nanocomposite

About: Polymer nanocomposite is a research topic. Over the lifetime, 8977 publications have been published within this topic receiving 297599 citations.

Dramatically enhanced mechanical performance of nylon-6 magnetic composites with nanostructured hybrid one-dimensional carbon nanotube-two-dimensional clay nanoplatelet heterostructures.

Abstract: Mechanically robust, magnetic nylon-6 nanocomposites reinforced by one-dimensional (1D) carbon nanotube (CNT)-two-dimensional (2D) clay nanoplatelet hybrids have been prepared using a simple melt-compounding technique. The direct iron-catalyzed chemical vapor deposition (CVD) growth of multiwalled CNTs utilizes iron oxide-immobilized clay nanoplatelets as substrates, carrying out in situ intercalation and exfoliation of clay nanoplatelets. By using such a hybridization and coexfoliation method, the as-obtained heterostructured hybrids used without any purification are demonstrated to be ideal and excellent nanofillers for mechanical reinforcement for fabricating nylon-6 nanocomposites, due to their homogeneous dispersion and strong interfacial interaction with the polymer matrix. The nucleation sites provided by the nanohybrids seem to be favorable to the formation of thermodynamically stable α-phase crystals of nylon-6 with much higher stiffness and hardness than γ-form of nylon-6, namely, a silicate-induced crystal transformation from the α-form to the γ-form of nylon-6 was greatly inhibited or "shielded" by the CNT-wrapped clay nanoplatelets. Furthermore, the nanostructured CNT-clay hybrid heterostructures containing residual iron oxide nanoparticles show novel magnetic properties in both bulk solids and polymer nanocomposites. Therefore, this can be probably developed into a facile and practical method to fabricate polymer nanocomposites with high performance and multifunctionality.

Transparent and luminescent YVO4 : Eu/polymer nanocomposites prepared by in situ polymerization

Abstract: We report the synthesis and characterization of transparent nanocomposites consisting of YVO4 : Eu nanoparticles in polymer matrices. The composite materials are made by in situ polymerization of particle dispersions in methyl methacrylate (MMA) and lauryl acrylate (LA). Two different pathways for the preparation of these dispersions and their polymerization are presented. The first method, based on reverse microemulsions, yields a dispersion of YVO4 : Eu nanoparticles in MMA. The microemulsion droplets function as space-confined containers for the precipitation reaction of YVO4 : Eu and their hydrodynamic diameter can be controlled in the range of 6–90 nm as measured by dynamic light scattering (DLS). When a microemulsion with a droplet size of 7 nm is used, nanoparticles with a crystallite size of 5.8 nm are obtained as determined from X-ray diffraction patterns. Crystalline particles are identified by transmission electron microscopy (TEM) in samples taken directly from the microemulsion. A phase transfer of YVO4 : Eu nanoparticles from an aqueous dispersion into nonpolar solvents is the key step for the second preparation method. A crystallite diameter of 5 nm was determined by XRD, while crystalline particles in the size range of 3–18 nm could be identified with TEM. The modified particles were dispersed in LA to give a clear dispersion. No aggregation or particle growth takes place during the steps of phase transfer, isolation and redispersion of the nanoparticles as confirmed by DLS and powder X-ray diffraction. Both particle dispersions in MMA and in LA were polymerized using an in situ polymerization approach resulting in solid nanocomposites with excellent optical properties. The obtained materials are highly transparent (transmission >90% at 600 nm), possess a low haze (0.7–1.4%) and show red photoluminescence upon UV excitation, due to the integration of luminescent YVO4 : Eu nanoparticles.

Interfacial Connection Mechanisms in Calcium-Silicate-Hydrates/Polymer Nanocomposites: A Molecular Dynamics Study.

Abstract: Properties of organic/inorganic composites can be highly dependent on the interfacial connections. In this work, molecular dynamics, using pair-potential-based force fields, was employed to investigate the structure, dynamics, and stability of interfacial connections between calcium-silicate-hydrates (C-S-H) and organic functional groups of three different polymer species. The calculation results suggest that the affinity between C-S-H and polymers is influenced by the polarity of the functional groups and the diffusivity and aggregation tendency of the polymers. In the interfaces, the calcium counterions from C-S-H act as the coordination atoms in bridging the double-bonded oxygen atoms in the carboxyl groups (-COOH), and the Ca-O connection plays a dominant role in binding poly(acrylic acid) (PAA) due to the high bond strength defined by time-correlated function. The defective calcium-silicate chains provide significant numbers of nonbridging oxygen sites to accept H-bonds from -COOH groups. As compared with PAA, the interfacial interactions are much weaker between C-S-H and poly(vinyl alcohol) (PVA) or poly(ethylene glycol) (PEG). Predominate percentage of the -OH groups in the PVA form H-bonds with inter- and intramolecule, which results in the polymer intertwining and reduces the probability of H-bond connections between PVA and C-S-H. On the other hand, the inert functional groups (C-O-C) in poly(ethylene glycol) (PEG) make this polymer exhibit unfolded configurations and move freely with little restrictions. The interaction mechanisms interpreted in this organic-inorganic interface can give fundamental insights into the polymer modification of C-S-H and further implications to improving cement-based materials from the genetic level.