Dresden 2014 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 29: Colloids and Complex Liquids I
CPP 29.12: Vortrag
Mittwoch, 2. April 2014, 12:30–12:45, ZEU 114
Structure and phase behavior of n-alkyl-PEO polymer micelles — •Matthias Amann, Lutz Willner, Jörg Stellbrink, Aurel Radulescu, and Dieter Richter — JCNS-1 & ICS-1, Forschungszentrum Jülich GmbH, D-52425 Jülich
We examine the structure of star-like n-alkyl-PEO polymer micelles in water as a function of polymer concentration with small-angle neutron scattering (SANS) methods. We present a temperature-quench-experiment to determine the aggregation number Nagg of the micelles in the semidilute regime, exploiting the well-known unimer exchange kinetics of our model system [1]. Furthermore, we investigate the phase behavior of the model system using high resolution SANS and discuss it with regard to a theoretical phase diagram for star-polymers, based on an ultrasoft interaction potential.
We found that the aggregation number Nagg = 100 of n-alkyl-PEO micelles is independent of polymer concentration, which contradicts theoretical considerations for star-like micelles predicting a strong increase of Nagg above the overlap concentration φ∗. Near the overlap concentration φ∗, a phase transition from liquid to a crystalline phase was observed. By analyzing the experimental structure factor of the polymer solutions, the crystalline phase could be identified as a fcc-crystal, which is in good agreement with theory.
References: [1] Zinn et al., Soft Matter 2012, 8, 623-626.