Sedimentation stability and aging of aqueous dispersions of Laponite in the presence of cetyltrimethylammonium bromide

Physico-Chemical Properties of Laponite®/Polyethylene-oxide Based Composites

This review aims to provide a literature overview as well as the authors' personal account to the studies of Laponite® (Lap)/Polyethylene-oxide (PEO) based composite materials and their applications. These composites can be prepared over a wide range of their mutual concentrations, they are highly water soluble, and have many useful physico-chemical properties. To the readers' convenience, the contents are subdivided into different sections, related with consideration of PEO properties and its solubility in water, behavior of Lap systems(structure of Lap-platelets, properties of aqueous dispersions of Lap and aging effects in them), analyzing ofproperties LAP/PEO systems, Lap platelets-PEO interactions, adsorption mechanisms, aging effects, aggregation and electrokinetic properties. The different applications of Lap/PEO composites are reviewed. These applications include Lap/PEO based electrolytes for lithium polymer batteries, electrospun nanofibers, environmental, biomedical and biotechnology engineering. Both Lap and PEO are highly biocompatible with living systems and they are non-toxic, non-yellowing, and non-inflammable. Medical applications of Lap/PEO composites in bio-sensing, tissue engineering, drug delivery, cell proliferation, and wound dressings are also discussed.

Electrokinetic Behavior of Laponite RD in Aqueous Suspensions Containing Poly(ethylene oxide) and Cetyltrimethylammonium Bromide

The aqueous suspensions of Laponite RD (Lap) platelets demonstrate rich phase diagrams. Both poly(ethylene oxide) (PEO) and cetyltrimethylammonium bromide (CTAB) molecules competitively adsorb on the surface of Lap, and strong interactions between PEO and CTAB exist. The stability of ternary systems Lap + PEO + CTAB can be finely regulated by changing the balance of these interactions. The electrokinetic technique was used to study 0.065 and 2% wt Lap suspensions in the presence of different amounts of PEO of various molecular masses M_w (400-20,000 g/mol) and CTAB (0-1 mM). For 0.065% wt Lap suspension, the additives of PEO did not affect the position of the isoelectric point (IEP), but the impact of PEO in the regions below or above the IEP was significant, especially for a large M_w. The observed effects were explained, accounting the model for the adsorption of PEO in the form of loops and tails as well as for the changes in the packing balance of CTAB and PEO on the surface of Lap. For 2% wt suspension, the strong effects of M_w on the ζ-potential and aggregation of particles were explained by screening the repulsive double layers by PEO chains, by bridging the Lap particles via PEO molecules, and by the impact of CTAB molecules on the bridging between Lap aggregates.

2D Nanoclay for Biomedical Applications: Regenerative Medicine, Therapeutic Delivery, and Additive Manufacturing

Clay nanomaterials are an emerging class of 2D biomaterials of interest due to their atomically thin layered structure, charged characteristics, and well-defined composition. Synthetic nanoclays are plate-like polyions composed of simple or complex salts of silicic acids with a heterogeneous charge distribution and patchy interactions. Due to their biocompatible characteristics, unique shape, high surface-to-volume ratio, and charge, nanoclays are investigated for various biomedical applications. Here, a critical overview of the physical, chemical, and physiological interactions of nanoclay with biological moieties, including cells, proteins, and polymers, is provided. The state-of-the-art biomedical applications of 2D nanoclay in regenerative medicine, therapeutic delivery, and additive manufacturing are reviewed. In addition, recent developments that are shaping this emerging field are discussed and promising new research directions for 2D nanoclay-based biomaterials are identified.

Mechanism of Methylene Blue adsorption on hybrid laponite-multi-walled carbon nanotube particles

The kinetics of adsorption and parameters of equilibrium adsorption of Methylene Blue (MB) on hybrid laponite-multi-walled carbon nanotube (NT) particles in aqueous suspensions were determined. The laponite platelets were used in order to facilitate disaggregation of NTs in aqueous suspensions and enhance the adsorption capacity of hybrid particles for MB. Experiments were performed at room temperature (298 K), and the laponite/NT ratio (Xl) was varied in the range of 0-0.5. For elucidation of the mechanism of MB adsorption on hybrid particles, the electrical conductivity of the system as well as the electrokinetic potential of laponite-NT hybrid particles were measured. Three different stages in the kinetics of adsorption of MB on the surface of NTs or hybrid laponite-NT particles were discovered to be a fast initial stage I (adsorption time t=0-10 min), a slower intermediate stage II (up to t=120 min) and a long-lasting final stage III (up to t=24hr). The presence of these stages was explained accounting for different types of interactions between MB and adsorbent particles, as well as for the changes in the structure of aggregates of NT particles and the long-range processes of restructuring of laponite platelets on the surface of NTs. The analysis of experimental data on specific surface area versus the value of Xl evidenced in favor of the model with linear contacts between rigid laponite platelets and NTs. It was also concluded that electrostatic interactions control the first stage of adsorption at low MB concentrations.