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Direct imaging of temperature-sensitive core-shell latexes by cryogenic transmission electron microscopy

Direct imaging of temperature-sensitive core-shell latexes by cryogenic transmission electron microscopy

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CRASSOUS, Jérôme J., Alexander WITTEMANN, Miriam SIEBENBÜRGER, Marc SCHRINNER, Markus DRECHSLER, Matthias BALLAUFF, 2008. Direct imaging of temperature-sensitive core-shell latexes by cryogenic transmission electron microscopy. In: Colloid and Polymer Science. 286(6-7), pp. 805-812. ISSN 0303-402X

@article{Crassous2008Direc-20191, title={Direct imaging of temperature-sensitive core-shell latexes by cryogenic transmission electron microscopy}, year={2008}, doi={10.1007/s00396-008-1873-3}, number={6-7}, volume={286}, issn={0303-402X}, journal={Colloid and Polymer Science}, pages={805--812}, author={Crassous, Jérôme J. and Wittemann, Alexander and Siebenbürger, Miriam and Schrinner, Marc and Drechsler, Markus and Ballauff, Matthias} }

2012-08-22T10:03:16Z Crassous, Jérôme J. deposit-license We present a comprehensive investigation of the volume transition in thermosensitive core-shell particles. The particles consist of a solid core of poly (styrene) (radius: 52 nm) onto which a network of crosslinked poly(N-isopropylacrylamide) (PNIPAM) is affixed. The degree of crosslinking of the PNIPAM shell effected by the crosslinker N,N'-methylenebisacrylamide was varied between 1.25 and 5 mol%. Immersed in water, the shell of these particles is swollen at low temperatures. Raising the temperature above 32◦C leads to a volume transition within the shell. Cryogenic transmission electron microscopy (Cryo-TEM) and dynamic light scattering (DLS) have been used to investigate the structure and swelling of the particles. The Cryo-TEM micrographs directly show inhomogeneities of the network. Moreover, a buckling of the shell from the core particle is evident. This buckling increases with decreasing degree of crosslinking. A comparison of the overall size of the particles determined by DLS and Cryo-TEM demonstrates that the hydrodynamic radius provides a valid measure for the size of the particles. The phase transition within the network measured by DLS can be described by the Flory–Rehner theory. It is shown that this model captures the main features of the volume transition within the core-shell particles including the dependence of the phase transition on the degree of crosslinking. All dispersions crystallize at volume fractions above 0.5. The resulting phase diagram is identical to the phase behavior of hard spheres within the limits of error. This demonstrates that the core-shell microgels can be treated as hard spheres up to volume fractions of at least 0.55. Schrinner, Marc Drechsler, Markus Siebenbürger, Miriam Schrinner, Marc Wittemann, Alexander Crassous, Jérôme J. eng Direct imaging of temperature-sensitive core-shell latexes by cryogenic transmission electron microscopy 2012-08-22T10:03:16Z First publ. in: Colloid & Polymer Science ; 286 (2008), 6/7. - pp. 805-812 Drechsler, Markus Ballauff, Matthias Siebenbürger, Miriam Wittemann, Alexander Ballauff, Matthias 2008

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