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Temperature and pH dependence of the catalytic activity of colloidal platinum nanoparticles stabilized by poly[(vinylamine)‐ co ‐( N‐ vinylisobutyramide)
Author(s) -
Chen ChunWei,
Arai Kumiko,
Yamamoto Kazuya,
Serizawa Takeshi,
Akashi Mitsuru
Publication year - 2000
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/1521-3935(20001201)201:18<2811::aid-macp2811>3.0.co;2-0
Subject(s) - catalysis , platinum , colloid , copolymer , polymer chemistry , aqueous solution , platinum nanoparticles , nanoparticle , chemistry , vinyl alcohol , particle size , flocculation , lower critical solution temperature , chemical engineering , materials science , polymer , nanotechnology , organic chemistry , engineering
Colloidal platinum nanoparticles in the size range of 5–35 Å have been successfully prepared in water at room temperature by NaBH 4 reduction of ionic platinum in the presence of poly[(vinylamine)‐ co ‐( N ‐vinylisobutyramide)] (PVAm‐ co ‐PNVIBA). To our knowledge, the temperature‐ and pH‐responsive copolymer was used for the first time as the stabilizer of colloidal metal particles. Three PVAm ‐co ‐PNVIBA copolymers with PVAm contents of 4.1, 8.3, and 19.8 mol‐% were examined. The particle size and morphology of the platinum colloids varied with the copolymer composition, as confirmed by TEM measurements. The polymer‐stabilized Pt nanoparticles precipitated on heating above their critical flocculation temperatures (CFTs), which were strongly dependent on the solution pH and the copolymer composition. The CFTs were 0.2–1.6°C lower than the lower critical solution temperatures (LCSTs) of the copolymers free in water and the differences increased with increasing PVAm content. The catalytic activity of the Pt nanoparticles was investigated in the aqueous hydrogenation of allyl alcohol. It was found that the activity was regulated through temperature‐ and pH‐induced phase separation. The PVAm content also strongly effected the catalytic activity and the morphology of phase separated catalysts. With a PVAm content of 4.1 mol‐%, the colloidal platinum sol reversibly changed its catalytic activity with changes in temperature.