Berlin 2015 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 8: Colloids and Complex Liquids II (joint session CPP, BP, DY)
CPP 8.6: Talk
Monday, March 16, 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)