Temperature dependent phase behavior of PNIPAM microgels in mixed water/methanol solvents |
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| Authors: | Hiroyuki Kojima Fumihiko Tanaka Christine Scherzinger Walter Richtering |
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| Affiliation: | 1. Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Kyoto 615-8510, Japan Institute of Theoretical Polymer Science, 5-19-2 Ozenji, Kawasaki, 215-0018 Japan;2. Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany |
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| Abstract: | Temperature dependent phase behavior of poly(N-isopropylacylamide) (PNIPAM) microgels in water/methanol mixtures of different composition was studied with dynamic light scattering (DLS) and small-angle neutron scattering (SANS). Using DLS, it is possible to measure the diffusion coefficient, and thus the size of particles exactly and directly; the variation of the phase transition temperature in the different solvents is also easy to detect by this method. With SANS measurements in D2O/MeOD mixtures, some of the DLS results were confirmed. Moreover, SANS measurements give valuable information on the particle structure in different solvents. The experiments were compared with the theory of competitive hydration introduced by Tanaka et al. We found a good agreement of theory and experiment, and obtained the theoretical predictions: around the transition temperature, the composition of the bound methanol along the chains is higher than that of the outer solution, while the whole methanol composition inside the gel is lower. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym. Phys. 2013, 51, 1100–1111 |
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| Keywords: | competitive hydrogen bonds cononsolvency dynamic light scattering microgels neutron scattering poly(N-isopropylacylamide) solvent excess adsorption solvent excess binding |
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