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Licensed Unlicensed Requires Authentication Published by De Gruyter (O) November 7, 2014

Comparison of the Microstructure of Stimuli Responsive Zwitterionic PNIPAM-co-Sulfobetaine Microgels with PNIPAM Microgels and Classical Hard-Sphere Systems

  • Andreas Josef Schmid EMAIL logo , Jonas Riest , Thomas Eckert , Peter Lindner , Gerhard Naegele and Walter Richtering

Abstract

In this study, we compare the experimental static structure factors of concentrated solutions of amphoteric poly(N-isopropylacrylamide) (PNIPAM) microgels with those of the polydisperse hard-sphere model. We use zwitterionic microgels as model systems for amphoteric microgels with an equal amount of positive and negative charges located in a defined distance. Using small angle neutron scattering (SANS), we measure the static structure factors, SM(q), of a series of zwitterionic microgels with increasing amount of zwitterion, including a reference sample of pure PNIPAM. The experimental SM(q) is compared with predictions based on the Percus-Yevick approximation for hard spheres. We also compare with the PNIPAM reference sample measured for zwitterionic microgels. We find no significant influence of the zwitterionic comonomer on the effective pair potential. The PNIPAM and the zwitterionic microgels can be described by the hard-sphere model for smaller volume fractions ϕT ≲ 0.4 only.

Received: 2014-6-30
Accepted: 2014-9-11
Published Online: 2014-11-7
Published in Print: 2014-12-28

©2014 Walter de Gruyter Berlin/Boston

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