Water-Dispersible Silica-Polyelectrolyte Nanocomposites Prepared via Acid-Triggered Polycondensation of Silicic Acid and Directed by Polycations.

The present work describes the acid-triggered condensation of silicic acid, Si(OH)₄, as directed by selected polycations in aqueous solution in the pH range of 6.5⁻8.0 at room temperature, without the use of additional solvents or surfactants.

Phase separation of aqueous poly(2-dimethylaminoethyl methacrylate-block-N-vinylcaprolactams).

Details of the phase separation of the poly(N-vinylcaprolactam) (PVCL) homopolymers and block copolymers of PVCL and poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) were studied in aqueous buffer solutions. Phase separation occurred at either one or two temperatures depending on pH. The lower critical solution temperature of PVCL can be fine-tuned by varying the molecular weight of the block, whereas the phase separation temperature of the PDMAEMA block is strongly dependent on pH.

Molecular engineering of fracture energy dissipating sacrificial bonds into cellulose nanocrystal nanocomposites.

Even though nanocomposites have provided a plethora of routes to increase stiffness and strength, achieving increased toughness with suppressed catastrophic crack growth has remained more challenging. Inspired by the concepts of mechanically excellent natural nanomaterials, one-component nanocomposites were fabricated involving reinforcing colloidal nanorod cores with polymeric grafts containing supramolecular binding units. The concept is based on mechanically strong native cellulose nanocrystals (CNC) grafted with glassy polymethacrylate polymers, with side chains that contain 2-ureido-4[1H]-pyrimidone (UPy) pendant groups.

Hydration and dynamic state of nanoconfined polymer layers govern toughness in nacre-mimetic nanocomposites.

Biological high-performance composites inspire to create new tough, strong, and stiff structural materials. We show a brittle-to-ductile transition in a self-assembled nacre-inspired poly(vinyl alcohol)/nanoclay composite based on a hydration-induced glass-to-rubber transition in the 2D-nanoconfined poly(vinyl alcohol) layers. The findings open routes to design dissipative toughening mechanisms to combine stiffness and strength in nanocomposites.

Surface initiated polymerization of a cationic monomer on inner surfaces of silica capillaries: analyte separation by capillary electrophoresis versus polyelectrolyte behavior.

[2-(Methacryloyl)oxyethyl]trimethylammonium chloride was successfully polymerized by surface-initiated atom transfer radical polymerization method on the inner surface of fused-silica capillaries resulting in a covalently bound poly([2-(methacryloyl)oxyethyl]trimethylammonium chloride) coating. The coated capillaries provided in capillary electrophoresis an excellent run-to-run repeatability, capillary-to-capillary and day-to-day reproducibility. The capillaries worked reliably over 1 month with EOF repeatability below 0.