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

Temperature-dependent Phase Behavior of the Thermoresponsive Polymer Poly(N-isopropylmethacrylamide) in Aqueous Solution

Dec 9, 2020, 2:30 PM
3h 30m
Online event

Online event

Speaker

Chia-Hsin Ko (E13, Physik-Department, Technische Universität München.)

Description

Compared to the widely-investigated poly(N-isopropylacrylamide) (PNIPAM), poly(N-isopropylmethacrylamide) (PNIPMAM) has a higher phase transition temperature (43 °C instead of 32 °C). PNIPMAM has a similar chemical structure as PNIPAM, but the additional methyl groups on its backbone may lead to steric hindrance and weaker intramolecular interactions. To understand how these effects affect the thermal and structural behavior of PNIPMAM aqueous solutions, we investigate the phase behavior of PNIPMAM in D2O using turbidimetry, differential scanning calorimetry, Raman spectroscopy, small-angle and very small-angle neutron scattering (at KWS-1 and KWS-3 at MLZ). The PNIPMAM solutions undergo first macroscopic phase transition, but the PNIPMAM chains only dehydrate 2~3 °C above TCP. The methyl groups in PNIPMAM give rise to a more compact local chain conformation than in PNIPAM. Moreover, physical crosslinks and loosely packed large-scale inhomogeneities and physical crosslinks appear already in the one-phase state. We assign these differences to enhanced attractive intermolecular interactions resulting from the hydrophobic methyl groups. In the two-phase state, PNIPMAM mesoglobules are larger and more hydrated than PNIPAM mesoglobules. This is attributed to the steric hindrance caused by the methyl groups, which weaken the intrapolymer interactions. Thus, the methyl groups in PNIPMAM chains play a crucial role in the thermal and structural behavior around the phase transition.

Primary authors

Chia-Hsin Ko (E13, Physik-Department, Technische Universität München.) Kora-Lee Claude (E13, Physik-Department, Technische Universität München.) Bart-Jan Niebuur (TUM Physik-Department E13) Florian Jung (Technische Universität München) Jia-Jhen Kang (Technical University of Munich) Dr Dirk Schanzenbach (Institut für Chemie, Universität Potsdam) Henrich Frielinghaus (JCNS) Lester Barnsley (Jülich Centre for Neutron Science) Vitaliy Pipich Baohu Wu (JCNS-MLZ, FZ Juelich) Alfons Schulte (University of Central Florida) Peter Müller-Buschbaum (TU München, Physik-Department, LS Funktionelle Materialien) Prof. André Laschewsky (Universität Potsdam, Institut für Chemie) Christine Papadakis (Technische Universität München, Physik-Department, Fachgebiet Physik weicher Materie)

Presentation materials

There are no materials yet.