Imaging the volume transition in thermosensitive core-shell particles by cryo-transmission electron microscopy |
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Authors: | Crassous Jérôme J Ballauff Matthias Drechsler Markus Schmidt Judith Talmon Yeshayahu |
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Institution: | Physikalische Chemie I, University of Bayreuth, 95440 Bayreuth, Germany. |
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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 degrees 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. |
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