Jump to main content
Jump to site search

Issue 23, 2009
Previous Article Next Article

Continuous and discontinuous volume-phase transitions in surface-tethered, photo-crosslinked poly(N-isopropylacrylamide) networks

Author affiliations

Abstract

The waterpolymer demixing behavior of surface-tethered poly(N-isopropylacrylamide) networks copolymerized with x mol% of photo-crosslinkable methacryloyloxybenzophenone (MaBP) (x = 1, 3, 5, 10%) was characterized with neutron reflection and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. Neutron reflection revealed that water is expelled discontinuously at low crosslink densities and continuously at high crosslink densities. The demarcation between the two behaviors occurred roughly at the critical point as measured by cloud point experiments. The neutron reflection experiments further revealed that the discontinuous concentration jump at low crosslink densities takes place in the presence of significant amounts of water and that water is not completely expelled in the process, with 2–3 water molecules remaining per polymer segment after the collapse of the network, independent of crosslink density. Parallel measurements with ATR-FTIR confirm that the transition is driven by dehydration of the isopropyl groups, with water remaining confined between the amide groups even at temperatures well above the demixing temperature. The internal water, however, is readily exchanged with deuterium oxide at temperatures up to 100 °C. This exchange points to the absence of a hydrophobic skin or physical barrier that would prevent water from completely leaving the film above the demixing temperature.

Graphical abstract: Continuous and discontinuous volume-phase transitions in surface-tethered, photo-crosslinked poly(N-isopropylacrylamide) networks

Back to tab navigation

Article information


Submitted
12 Mar 2009
Accepted
27 Jul 2009
First published
22 Sep 2009

Soft Matter, 2009,5, 4733-4738
Article type
Paper

Continuous and discontinuous volume-phase transitions in surface-tethered, photo-crosslinked poly(N-isopropylacrylamide) networks

A. Vidyasagar, H. L. Smith, J. Majewski and R. G. Toomey, Soft Matter, 2009, 5, 4733
DOI: 10.1039/B904963K

Social activity

Search articles by author

Spotlight

Advertisements