Polystyrene latex particles coated with crosslinked polyN-isopropylacrylamideReportar como inadecuado

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Colloid and Polymer Science

, Volume 284, Issue 11, pp 1255–1263

First Online: 18 March 2006Received: 09 November 2005Accepted: 09 February 2006


Thermoresponsive colloidal particles were prepared by seeded precipitation polymerization of N-isopropylacrylamide NIPAM in the presence of a crosslinking monomer, N,N-methylenebisacrylamide MBA, using polystyrene latex particles ca. 50 nm in diameter as seeds in aqueous dispersion. Phase transitions of the prepared polyN-isopropylacrylamide, PNIPAM, shells on polystyrene cores were studied in comparison to colloidal PNIPAM microgel particles, in H2O and-or in D2O by dynamic light scattering, microcalorimetry and by H NMR spectroscopy including the measurements of spin–lattice T1 and spin–spin T2 relaxation times for the protons of PNIPAM. As expected, the seed particles grew in hydrodynamic size during the crosslinking polymerization of NIPAM, and a larger NIPAM to seed mass ratio in the polymerization batch led to a larger increase of particle size indicating a product coated with a thicker PNIPAM shell. Broader microcalorimetric endotherms of dehydration were observed for crosslinked PNIPAM on the solid cores compared to the PNIPAM microgels and also an increase of the transition temperature was observed. The calorimetric results were complemented by the NMR spectroscopy data of the H-signal intensities upon heating in D2O, showing that the phase transition of crosslinked PNIPAM on polystyrene core shifts towards higher temperatures when compared to the microgels, and also that the temperature range of the transition is broader.

KeywordsPolyN-isopropylacrylamide Microgel Core-shell H NMR Microcalorimetry  Download fulltext PDF

Autor: Mirja Andersson - Sami Hietala - Heikki Tenhu - Sirkka Liisa Maunu

Fuente: https://link.springer.com/

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