Yongtao Wu

Designable synthesis of nanocomposite hydrogels with excellent mechanical properties based on chemical cross-linked interactions

A new type of nanocomposite hydrogels based on covalent cross-linked interactions with excellent mechanical properties and good stability has been prepared by using in situ free-radical polymerization; polystyrene nanoparticles with photo-activity are used as the cross-linking agent.

Preparation and Property of Poly(N-isopropylacrylamide) (PNIPAAm)/Clay/Linear Polyacrylamide (PAAm) Nanocomposite Hydrogels

In this study, a linear polyacrylamide (PAAm) with an average viscosimetric molecular weight 3.97 × 103 kg mol−1 was added to the prereaction solution for the preparation of poly(N-isopropylacrylamide) (PNIPAAm)/clay nanocomposite hydrogels. The effects of the linear PAAm on the optical transparency and tensile property of the resulting PNIPAAm/clay/linear PAAm hydrogels were systematically investigated. The results revealed that the optical transparency and mechanical tensile properties of the resultant hydrogels strongly depended on the linear PAAm content. In particular, 5 wt% loading of linear PAAm led to almost fivefold decreases of transmittance at 25°C and a onefold increase of the tensile elongation at break. These characteristic changes were explained by a typical interpenetrating microstructure, which was formed by PNIPAAm due to the incorporation of linear PAAm in the PNIPAAm/clay network. The dynamic rheological test and infrared spectroscopy analysis on the mixed solutions consisting of linear PAAm and clay platelets further confirmed the interaction.

Responsive P(NIPAM-co-AA) Particle-Functionalized Magnetic Microspheres

Functionalized magnetic microspheres were prepared by anchoring cross-linked core–shell poly(N-isopropylacrylamide-co-acrylic acid) (P(NIPAM-co-AA)) nanoparticles onto silica-coated magnetic microspheres (Fe3O4@SiO2). First, the smaller polystyrene/P(NIPAM-co-AA) core–shell nanoparticles were synthesized through seed emulsion polymerization and adhered to the surface of amino-modified Fe3O4@SiO2 micorspheres, which were made using the modified Stober method through electrostatic interaction under appropriate preparation conditions. An amidation reaction between the carboxylic and amino groups on the respective surfaces was then catalyzed. Finally, the novel architecture magnetic microspheres with multiresponsive functionalities were obtained, and their polymerization conditions, environmental sensitivity, and magnetic properties were discussed and optimized. The superparamagnetism and temperature/pH dual responsivity and excellent dispersibility of the P(NIPAM-co-AA) functionalized magnetic microspheres provide them with high potential to be used in the fields of controlled drug delivery, bioseparation, and catalysis.