This title appears in the Scientific Report : 2020 

Revealing the Aggregation Mechanism, Structure, and Internal Dynamics of Poly(vinyl alcohol) Microgel Prepared through Liquid–Liquid Phase Separation
Perfetti, Marco
Gallucci, Noemi / Russo Krauss, Irene / Radulescu, Aurel / Pasini, Stefano / Holderer, Olaf / D’Errico, Gerardino / Vitiello, Giuseppe / Bianchetti, Giulia Ottavia / Paduano, Luigi (Corresponding author)
Neutronenstreuung ; Neutronenstreuung; JCNS-1
Heinz Maier-Leibnitz Zentrum; MLZ
Macromolecules, 53 (2020) 3, S. 852 - 861
Washington, DC Am. Chem. Soc. 2020
Journal Article
Jülich Centre for Neutron Research (JCNS)
Soft Matter, Health and Life Sciences
Published on 2020-01-21. Available in OpenAccess from 2021-01-21.
Published on 2020-01-21. Available in OpenAccess from 2021-01-21.
Please use the identifier: in citations.
Please use the identifier: in citations.
The use of technologies based on soft polymer particles represents an effective way to deliver target molecules with a specific function. To design a well-performing delivery system, it is fundamental to rationalize both the aggregation and the structural properties of such particles. In this study, we present the kinetic and structural characterization over time of poly(vinyl alcohol) (PVA) microgels obtained through a salting-out process in the presence of NaCl. We have analyzed how both the polymer and salt concentrations affect the aggregation process. The aggregation rate as well as the morphology and physico-chemical parameters, such as mass and chain density of the microgels, have been determined through static and dynamic light scattering and discussed in the framework of the diffusion-limited and reaction-limited colloid aggregation. Insights into the polymer chain arrangements and their dynamics have been gained by means of small-angle neutron scattering and neutron spin-echo measurements. As a result, it was found that NaCl induces a liquid phase separation in solution with the formation of spherical PVA microaggregates, which grow under a reaction-limited aggregation mechanism. The particles increase their size and compactness over time. Within the aggregate, the polymer chains are locally organized to form randomly oriented lamellae with a thickness of about 60 Å. The internal dynamics is a complex mixture of diffusion, Zimm dynamics, and possibly effects from crowding with the transition to a Rouse-like behavior. The microparticle preparation based on the salting-out process constitutes a novelty, if compared to the methods already existing and based on the use of chemical cross-linkers, and is a cheap and easy protocol that allows tuning both particle size and density by varying the salt concentration.