SAXS Investigation of the Effect of Temperature on the Multiscale Structure of a Macroporous Poly(N-isopropylacrylamide) Gel

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Chalal M., Ehrburger-Dolle F., Morfin I., Bley F., Aguilar de Armas M., Lopez Donaire M., ...More

MACROMOLECULES, vol.43, no.4, pp.2009-2017, 2010 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 43 Issue: 4
  • Publication Date: 2010
  • Doi Number: 10.1021/ma902655h
  • Journal Name: MACROMOLECULES
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.2009-2017
  • Hacettepe University Affiliated: Yes

Abstract

The temperature-induced structural modifications of poly(N-isopropylacrylamide) hydrogel (pNIPA) were investigated by small-angle X-ray scattering (SAXS) over a broad range of q values (3.5 x 10(-2)-12 nm(-1)) at temperatures ranging between 18 and 37 degrees C. The sample Studied was claborated by cryopolymerization yielding a macroporous gel (cryogel). The pNIPA gel forms the walls (the thickness at 23 degrees C is about 12 mu m). The SAXS curves display an isoscattering (or isosbestic) point located at q(iso) = 3.633 nm(-1) and disappearingabovc 30 degrees C. This feature has never been reported up to now. The SAXS curves obtained at each temperature are well fitted by a sum of four equations describing respectively the scattering resulting from the gel surface (power law), from the solidlike (Guinier equation) and liquidlike (Ornstein - Zernike equation) heterogeneities, and from the chain-chain correlation yielding a broad peak (pseudo-Voigt equation) in the high-q domain. The temperature dependence of the parameters obtained from the fit is analyzed and discussed.