Dresden 2014 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 56: Colloids and Complex Liquids IV
CPP 56.4: Talk
Friday, April 4, 2014, 10:15–10:30, ZEU 260
Dehydration behavior of phase separating PNIPAM solutions — •Martine Philipp1, Konstantinos Kyriakos1, Luca Silvi1,2, Wiebke Lohstroh1,2, Winfried Petry1,2, Jan K. Krüger3, Christine M. Papadakis1, and Peter Müller-Buschbaum1 — 1TU München, Physik-Department, LS Funktionelle Materialien/FG Physik weicher Materie, Garching, Germany — 2TU München, MLZ, Garching, Germany — 3Université du Luxembourg, LPM, Luxembourg, Luxembourg
A structural instability leads to the collapse and aggregation of poly(N-isopropyl acrylamide) (PNIPAM) in aqueous environment at an LCST-type demixing transition. This transition is provoked by the interplay of H-bond and hydrophobic interactions between PNIPAM and water. The cooperative dehydration of PNIPAM plays a key role for the genesis of the PNIPAM-rich globules. Using quasi-elastic neutron scattering, we elucidate for the first time the partial dehydration process of PNIPAM in a concentrated solution. As the hydration number decreases from 8 to 2 during phase separation, the PNIPAM-rich globules contain at most 75 mass% PNIPAM. First insights into the relationship between the molecular dehydration process and the ensuing macroscopic changes of order parameter susceptibilities are presented for dilute to concentrated PNIPAM solutions, studying the volume expansion coefficient and compressibility [1,2].
[1] M. Philipp et al., Soft Matter 8, 11387 (2012)
[2] M. Philipp et al., Soft Matter 9, 5034 (2013)