Over the last decade smart microgels have been increasingly recognized as potential building blocks for photonic materials, catalytic carriers and sensors.[1] This applicability is based on the fairly unlimited tuning possibilities of swelling properties as well as scattering properties of those particles. The present contribution studies non-(N-isopropyl acrylamide)-based core-shell microgels that exhibit a linear thermoresponsive behavior in a temperature range between 25°C and 40°C. It is the combination of distinct materials in core and shell, that gives the particles this unique property. For the first part of our study we synthesized statistical copolymers from N-n-proplyacrylamide (NNPAM) and N-isopropylmethacrylamide (NIPMAM) and study their behavior by means of scattering techniques [2]. Moreover, we have synthesized core-shell microgels from these monomers with differently cross-linked cores. This approach was inspired by the work of the Richtering group[3]. Photon correlation spectroscopy allowed us to study the temperature dependent swelling, which revealed a significant influence of the core properties on the overall core-shell behavior. A major finding of these experiments is that the swelling becomes linear dependent on temperature and the crosslinker content of the core is directly related to the linear response. The core-shell particles behave piezo-like and might have potential as actuators [4]. The internal structure of the particles is followed by means of small angle neutron scattering (SANS) revealing heterogeneities during the transitions of the NNPAM shell.
[1] A. Fernandez-Nieves, H. Wyss, J. Mattsson and D. Weitz, Microgel Suspensions, Wiley VCH, Weinheim, Germany, 2011
[2] B. Wedel, M. Zeiser, and T. Hellweg, Zeitschrift f. Physikalische Chemie, 2012, 226, 737748
[3] I. Berndt and W. Richtering Macromolecules 2003, 36, 8780
[4] M. Zeiser, I. Freudensprung, and T. Hellweg, Polymer, 2012, 53,6096
thomas.hellweg@uni-bielefeld.de
