Microphase separation of stimuli-responsive interpenetrating network microgels investigated by scattering methods
EY Kozhunova and VY Rudyak and X Li and M Shibayama and GS Peters and OV Vyshivannaya and IR Nasimova and AV Chertovich, JOURNAL OF COLLOID AND INTERFACE SCIENCE, 597, 297-305 (2021).
Polymer stimuli-responsive microgels find their use in various applications. The knowledge of its internal structure is of importance for further improvement and expanding the scope. Interpenetrating network (IPN) microgels may possess a remarkable feature of strongly non-uniform inner architecture, even microphase separation, in conditions of a selective solvent. In this research, we, for the first time, use a combination of static light scattering (SLS) and small-angle X-ray scattering (SAXS) techniques to collect the structure factors of aqueous dispersions of poly(N-isopropylacrylamide)-polyacrylic acid IPN microgels on the broad scale of q values. We study the influence of solvent quality on microgel conformations and show that in a selective solvent, such a system undergoes microphase separation: the sub-network in a poor solvent conditions forms dense small aggregates inside the large swollen sub-network in a good solvent. We propose the microstructured sphere model for the IPN microgel structure factor interpretation and perform additional analysis and verification through coarse-grained molecular dynamics computer simulations. (c) 2021 Elsevier Inc. All rights reserved.
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