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DY: Fachverband Dynamik und Statistische Physik

DY 11: Colloids and Complex Liquids II (joint session CPP/ DY)

DY 11.6: Vortrag

Montag, 16. März 2015, 16:15–16:30, C 130

Cononsolvency in P(S-b-NIPAM) diblock copolymers - a time-resolved SANS study of the aggregation process — Konstantinos Kyriakos¹, Martine Philipp¹, Joseph Adelsberger¹, Sebastian Jaksch¹, Anatoly V. Berezkin¹, Dersy M. Lugo², Walter Richtering², Isabelle Grillo³, Anna Miasnikova⁴, André Laschewsky⁴, Peter Müller-Buschbaum¹, and •Christine M. Papadakis¹ — ¹TU München, Physik-Department, Garching — ²RWTH Aachen University, Institut für Physikalische Chemie — ³Institut Laue-Langevin, Grenoble, France — ⁴Universität Potsdam, Institut für Chemie, Potsdam-Golm

In mixtures of water and methanol, the thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) exhibits the cononsolvency effect, i.e. an enhanced tendency for phase separation at certain solvent compositions. We investigate the effect of adding methanol to (i) micellar solutions of polystyrene-b-poly(N-isopropylacrylamide) (PS-b-PNIPAM) diblock copolymers and (ii) PNIPAM homopolymers in D₂O using a stopped-flow instrument. The structural changes on mesoscopic length scales were followed by time-resolved small-angle neutron scattering (TR-SANS) with a time resolution of 0.1 s. In both systems, the pathway of the aggregation depends on the content of deuterated methanol; however, it is fundamentally different for homopolymer and diblock copolymer solutions. We propose a logarithmic coalescence model based on an energy barrier which is proportional to the aggregate radius.

1. Kyriakos et al., Macromolecules 47, 6867 (2014)