Dresden 2014 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 29: Colloids and Complex Liquids I

CPP 29.7: Talk

Wednesday, April 2, 2014, 11:15–11:30, ZEU 114

Birefringence Analysis of the Effect of Electric Fields on the Order-Disorder Transition Temperature in Concentrated Solutions of Block-Copolymers — •Christine Kathrein, Christian Pester, Heiko Schoberth, and Alexander Böker — Lehrstuhl für Makromolekulare Materialien und Oberflächen, DWI an der RWTH Aachen e.V., RWTH Aachen University, D-52056 Aachen, Germany

The application of electric fields is known to stabilize the disordered phase in concentrated solutions of lamellae forming block copolymers.

We address the fundamentally-important problem of the effect of dc electric fields on the order-disorder transition (ODT) temperature in microphase separated systems by performing in-situ birefringence measurements, and we compare this approach with the conventional high-throughput small angle X-ray scattering (SAXS) method. We studied concentrated solutions of block-copolymers in non-selective solvents with varied chemical- and volume composition. For both lamella and cylinder forming block-copolymers heating through the ODT temperature is accompanied by a continuous decrease in phase retardation. Birefringence has the advantage of being a non-destructive, facile method with high-throughput capacity. Moreover, the method has a very high sensitivity in detecting small thermal changes allowing a precise determination of the phase transition temperature.

The effect of various parameters such as dielectric contrast, chain length, solvent polarity and heating rate on the electric field induced shift of the ODT temperature is evaluated. Reported results provide new insights into the physics of confined chains under external fields.