Dec 8 – 10, 2020 Online only
Online event
Europe/Berlin timezone

Cononsolvency-induced collapse transitions in thermo-responsive block copolymer films

Dec 10, 2020, 3:45 PM
15m
Online event

Online event

Talk DN: Soft Matter DN2020. Soft Matter

Speaker

Christina Geiger (Technical University of Munich, Chair of Functional Materials)

Description

The diblock copolymer PMMA-b-PNIPAM forms micelles in solution that feature a permanently hydrophobic core and a thermo-responsive shell. While a typical shell collapse transition can be induced via a temperature stimulus at the LCST, the PNIPAM block is also sensitive to the composition of the surrounding solvent. Although water and organic cosolvents individually act as good solvents to the PNIPAM chain, mixtures of both act as bad solvent. As a consequence, the transition temperature shifts as a function of the molar fraction of the cosolvent. For PNIPAM, well-known examples of cosolvents include simple alcohols such as methanol or ethanol as well as acetone. We demonstrate that the cononsolvency effect is transferrable from solution to thin film systems. PMMA-b-PNIPAM films swollen in saturated water vapor show a swelling and collapse at the exchange of the surrounding atmosphere to a mixed vapor of water and cosolvent. The film kinetics are investigated with a focus on time-of-flight neutron reflectometry (TOF-NR) and spectral reflectance techniques. In order to differentiate between water and cosolvent distributions along the films’ vertical, sequential experiments with deuterated and non-deuterated water and cosolvent are performed. Complementary FTIR measurements reveal the hydration and cosolvent exchange process at the PNIPAM amide and alkyl functional groups.

Primary author

Christina Geiger (Technical University of Munich, Chair of Functional Materials)

Co-authors

Julija Reitenbach Lucas Kreuzer (TU München, Physik Department, E13) Tobias Widmann (TU München, Physik Department, LS Funktionelle Materialien) Peixi Wang (Workgroup Polymer Interfaces, TUM Department of Physics, Technical University of Munich) Dr Robert Cubitt Ms Cristiane Henschel (Universität Potsdam) Prof. André Laschewsky (Universität Potsdam) Christine Papadakis (Technische Universität München, Physik-Department, Fachgebiet Physik weicher Materie) Peter Müller-Buschbaum (TU München, Physik-Department, LS Funktionelle Materialien)

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