Phase separation in semidilute aqueous poly(N-isopropylacrylamide) solutions

Andreas Meier-Koll, Vitaliy Pipich, Peter Busch, Christine M. Papadakis, Peter Müller-Buschbaum

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60 Scopus citations

Abstract

The phase separation mechanism in semidilute aqueous poly(N- isopropylacrylamide) (PNIPAM) solutions is investigated with small-angle neutron scattering (SANS). The nature of the phase transition is probed in static SANS measurements and with time-dependent SANS measurements after a temperature jump. The observed critical exponents of the phase transition describing the temperature dependence of the Ornstein-Zernike amplitude and correlation length are smaller than values from mean-field theory. Time-dependent SANS measurements show that the specific surface decreases with increasing time after a temperature jump above the phase transition. Thus, the formation of additional hydrogen bonds in the collapsed state is a kinetic effect: A certain fraction of water remains as bound water in the system. Moreover, H-D exchange reactions observed in PNIPAM have to be taken into account.

Original languageEnglish
Pages (from-to)8791-8798
Number of pages8
JournalLangmuir
Volume28
Issue number23
DOIs
StatePublished - 12 Jun 2012

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