Search results for " PNIPAAM"

Temperature-responsive inclusion complex of cationic PNIPAAM diblock copolymer and γ-cyclodextrin

2012

Aqueous mixtures of γ-cyclodextrin (γ-CD) and the thermosensitive cationic diblock copolymer poly(N-isopropylacrylamide)-b-poly(3-acrylamidopropyl)trimethylammonium chloride (PNIPAAM24-b-PAMPTAM(+)9) or the PNIPAAM homopolymer PNIPAAM47 have been investigated using various experimental methods. Solid γ-CD–polymer inclusion complexes (pseudopolyrotaxanes) form at ambient temperatures in fairly concentrated CD solutions. The NMR measurements showed that the stoichiometry of the inclusion complexes is close to two NIPAAM units per CD molecule. The cationic block of the copolymer is not incorporated into the CD cavity. Synchrotron radiation X-ray diffraction spectra of the solid inclusion compl…

Biocompatible Poly(N-isopropylacrylamide)-halloysite Nanotubes for Thermoresponsive Curcumin Release

2015

The grafting of poly(N-isopropylacrylamide) (PNIPAAM) onto the halloysite external surface is proposed in order to obtain a novel thermoresponsive drug carrier for curcumin delivery. The new nanomaterial is characterized by means of FT-IR spectroscopy, thermogravimetric analysis, and SEM investigations. A high density of polymer chain was achieved at the nanoparticle surface. The PNIPAAM dehydration phenomenon was observed in water above 32 °C that is nearly coincident with the lower critical solution temperature for the polymer. The colloidal stability as well as the wettability of the obtained nanomaterial may be triggered by temperature stimuli. In vitro tests simulating the gastro-intes…

Halloysite Nanotubes as Support for Metal-Based Catalysts

Halloysite nanotubes (HNTs) are a natural, biocompatible, environmental friendly and cheap double-layered aluminosilicate mineral that has a predominantly hollow tubular structure. The general stoichiometry of halloysite is Al2Si2O5·4(H2O). The layer units consist of a tetrahedral SiOH sheet stacked with an edge shared octahedral AlO6 sheet with an internal aluminol group AlOH. A water layer exists between the adjacent two layers. Thanks to their structural features, HNTs are suitable for a potential application as support for catalytic composites. Recently, we reported the synthesis of novel palladium-based catalytic systems using halloysite nanotubes modified with imidazolium or triazoliu…

Design of PNIPAAM covalently grafted on halloysite nanotubes as a support for metal-based catalysts

2016

A thermo-responsive polymer such as poly(N-isopropylacrylamide) (PNIPAAM) was covalently grafted on the external surface of halloysite nanotubes (HNTs) by means of microwave irradiation. This nanomaterial was used as a support and stabilizer for palladium nanoparticles. The obtained HNT–PNIPAAM/PdNPs was characterized by means of TGA, SEM, EDS and TEM analyses. The palladium content of the catalyst was estimated to be 0.4 wt%. The stability of the catalytic material at different temperatures (below and above the PNIPAAM lower critical solution temperature) was tested in the Suzuki reaction under microwave irradiation. In addition, TEM analysis after five consecutive runs was performed. The …