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Thermoresponsive polymer microgels and small-angle scattering - a perfect match

Peter Schurtenberger, Division of Physical Chemistry and Lund Institute of advanced Neutron and X-ray Science LINXS, Lund University, Sweden

2019.05.21 | Trine Møller Hansen

Date Tue 18 Jun
Time 13:50 14:15
Location iNANO AUD (1593-012), Gustav Wieds Vej 14, 8000 Aarhus C

Peter Schurtenberger, Division of Physical Chemistry and Lund Institute of advanced Neutron and X-ray Science LINXS, Lund University, Sweden

Thermoresponsive polymer microgels and small-angle scattering - a perfect match

Responsive colloids such as thermo- or pH-sensitive microgels are ideal model systems to investigate the relationship between the nature of interparticle interactions and the plethora of self-assembled structures that can form in colloidal suspensions. They allow for a variation of the form, strength and range of the interaction potential almost at will. Moreover, due to their soft nature, we can create dispersions with concentrations far above random close packing. These ultra-dense suspensions exhibit fascinating flow properties and can form a variety of different amorphous and crystalline structures [1-3]. However, while the responsiveness and softness of these particles result in intriguing properties, they also pose considerable problems when attempting to characterize the response of individual particles to their environment at high packing fractions, where particles can adapt their shape, de-swell as well as partially interpenetrate. Here I will demonstrate how we can use small-angle scattering techniques as an ideal set of tools to obtain in-situ information about the structure of the individual particles as well as that of the assembled arrays on all relevant length scales. These experiments provide for example detailed information such as the internal density profile of the individual microgel and its response to various stimuli and packing fractions, and the structural correlations between particles in the different fluid and solid states. I will highlight in particular the use of small-angle neutron scattering together with appropriate contrast variation experiments, and combined with complementary techniques such as small-angle x-ray scattering and confocal microscopy, in order to obtain a quantitative understanding of the structural properties of dense and highly correlated microgel suspensions [4,5].

References:
[1] P. Mohanty, D. Paloli, J. Crassous, and P. Schurtenberger, in “Hydrogel Micro- and Nanoparticles”, L. Andrew Lyon and Michael J. Serpe, Eds., Wiley VCH, ISBN 978-3-527-33033-1, pp 369 - 396 (2012)
[2] P. S. Mohanty, P. Bagheri, S. Nöjd, A. Yethiraj and P. Schurtenberger, Phys. Rev. X 5 (2015) 011030
[3] T. Colla, P. S. Mohanty, S. Nöjd, E. Bialik, A. Riede, P. Schurtenberger, and C. N. Likos, ACS Nano 12, 4321 (2018)
[4] P. S. Mohanty, S.Nöjd, K. van Gruijthuijsen, J. J. Crassous, M. Obiols-Rabasa, R. Schweins, A. Stradner, and P. Schurtenberger, Scientific Reports 7, 1487 (2017)
[5] S. Nöjd, P. Holmqvist, N. Boon, M. Obiols-Rabas P. S. Mohanty, R. Schweins, and P. Schurtenberger, Soft Matter 14, 4150 (2018).


The lecture is part of the symposium Recent progress in small-angle scattering from soft matter and biological systems on the occasion of Professor Jan Skov Pedersen's 60th birthday.      

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