Issue 41, 2013

Kinetic processes at the demixing transition of PNIPAM solutions

Abstract

Kinetic processes, which are joined with mass transport, are studied in the vicinity of the sharp LCST-type demixing transition of semi-dilute aqueous poly(N-isopropyl acrylamide) (PNIPAM) solutions. These processes are slow as compared to the highly cooperative collapse of individual polymer chains. Purely elastic properties, that are particularly sensitive to this phase transition, are addressed depending on the temperature, space and time by Brillouin spectroscopy. Above the demixing temperature Tc, we discriminate between kinetics related to the phase separation into PNIPAM-rich and PNIPAM-poor domains and kinetics connected to the impact of gravitation on the on-going phase separation. Using shallow temperature jumps of 0.3 °C, the growth of compact PNIPAM-rich agglomerates with identical gel-like mechanical consistency is provoked independently of temperature and position within the sample above Tc. Astonishingly, the transition temperature does not vary while heating or cooling the solutions across the phase transition, although the elastic properties depend strongly on space and time during the equilibration of PNIPAM concentration gradients following the re-entrance into the low-temperature phase.

Graphical abstract: Kinetic processes at the demixing transition of PNIPAM solutions

Article information

Article type
Paper
Submitted
13 May 2013
Accepted
22 Aug 2013
First published
23 Aug 2013

Soft Matter, 2013,9, 9887-9896

Kinetic processes at the demixing transition of PNIPAM solutions

M. Philipp, U. Müller, R. J. Jiménez Riobóo, R. Sanctuary, P. Müller-Buschbaum and J. K. Krüger, Soft Matter, 2013, 9, 9887 DOI: 10.1039/C3SM51333E

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements