Dresden 2014 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 56: Colloids and Complex Liquids IV

CPP 56.3: Vortrag

Freitag, 4. April 2014, 10:00–10:15, ZEU 260

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, Isabelle Grillo², Anna Miasnikova³, André Laschewsky³, Peter Müller-Buschbaum¹, and Christine M. Papadakis¹ — ¹TU München, Physik-Department, Garching — ²Institut Laue-Langevin, Grenoble, France — ³Universität 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. The amount of cononsolvent may have a severe effect on the pathway of the collapse of the PNIPAM chain and the subsequent aggregation into mesoglobules, in line with previous experiments where aqueous solutions of PNIPAM were heated through the cloud point.

We report here on time-resolved small-angle neutron scattering experiments during the rapid addition of methanol to aqueous solutions of P(S-b-NIPAM). These block copolymers form core-shell micelles with a thermoresponsive shell. Small aggregates are formed very rapidly and growth with time reaching a certain size. The kinetics of this aggregation path depends on the amount of methanol. The observed growth process can be adequately described by the diffusion-limited coalescence model, and proceeds in a different way than previously observed in temperature jumps across the cloud point [1].

[1] Adelsberger, J. et al. Soft Matter 9, 1685 (2013)