Imaging the Volume Transition in Thermosensitive Core−Shell Particles by Cryo-Transmission Electron Microscopy
- 18 February 2006
- journal article
- Published by American Chemical Society (ACS) in Langmuir
- Vol. 22 (6), 2403-2406
- https://doi.org/10.1021/la053198f
Abstract
We report a study of colloidal thermosensitive core−shell particles by cryo-transmission electron microscopy (cryo-TEM). The particles consist of a solid core of poly(styrene), onto which a network of cross-linked poly(N-isopropylacrylamide) (PNIPAM) is affixed. In water, the shell of these particles swells when the temperature is low. Raising the temperature above 32 °C leads to a marked shrinking of the shell. In this letter, we present the first study of these core−shell particles by cryo-TEM in situ, that is, in aqueous solution. We demonstrate that the core−shell particles are well-defined and exhibit a narrow size distribution. In particular, the PNIPAM shell is compact and has a defined outer surface of a slightly irregular shape. The micrographs show that there are density fluctuations within the network. Cryo-TEM of the system above and below the transition temperature furnishes information about the thermosensitive particles that had not been available through other methods employed in previous investigations.Keywords
This publication has 27 references indexed in Scilit:
- Multicompartment Micelles from ABC Miktoarm Stars in WaterScience, 2004
- Shell-Restricted Swelling and Core Compression in Poly(N-isopropylacrylamide) Core−Shell MicrogelsMacromolecules, 2003
- Structural modifications in the swelling of inhomogeneous microgels by light and neutron scatteringPhysical Review E, 2002
- Digital cryogenic transmission electron microscopy: an advanced tool for direct imaging of complex fluidsColloids and Surfaces A: Physicochemical and Engineering Aspects, 2001
- Analysis of thermosensitive core–shell colloids by small-angle neutron scattering including contrast variationPhysical Chemistry Chemical Physics, 2001
- Rheology of a Temperature Sensitive Core−Shell LatexLangmuir, 1998
- Observation of the Volume Transition in Thermosensitive Core−Shell Latex Particles by Small-Angle X-ray ScatteringMacromolecules, 1998
- Small angle neutron scattering study on poly(N-isopropyl acrylamide) gels near their volume-phase transition temperatureThe Journal of Chemical Physics, 1992
- A novel approach for preparation of pH-sensitive hydrogels for enteric drug deliveryJournal of Controlled Release, 1991
- Cryo-electron microscopy of virusesNature, 1984