The Hsiao group at Stony Brook has been collaborating with scientists from ExxonMobil in the past two decades and developed a wide range of synchrotron X-ray scattering techniques for in-situ polymer studies. These techniques, including simultaneous SAXS/WAXS, rheo/X-ray, fiber/film spinning/deformation, have become powerful tools for the polymer community to engage cutting-edge research on polymer crystallization, orientation-induced phase transitions and hierarchical structural changes in semicrystalline polymers, block copolymers, nanocomposites, complex fluids, structured gels and biological systems. Recently, the Hsiao group and the Treesearch group at KTH have begun to jointly investigate some fundamental aspects of nanocellulose, the elementary building block of any plant cells. These nanometer-sized building blocks can be re-assembled into new bio-based nanostructured materials through hydrodynamic alignment. In this talk, we will demonstrate some examples of how SAXS/WAXS techniques have been utilized to target many fundamental aspects of nanocellulose as well as resolve structural transitions in time through in-situ experiments. In the first highlighted study, we have used SAXS/WAXS to study the cross-section of cellulose nanofibrils (CNF) in detail. With a new fitting methodology, we are able to demonstrate how CNF seem to consist of 2-4 elementary fibrils with 18 cellulose polymer chains. In the second highlighted study, we have used in-situ scanning SAXS/WAXS to study the ion-induced gel-transition of nanocellulose. With a custom-built flow-focusing mixing cell, spatial positions in the flow can be converted to time instances of the gel-transition. The experimental results provide a very clear and comprehensive view of how ions diffuse and induce gelation either by screening the charges of the oxidized nanocellulose or act as cross-linkers depending on ion valency.

Synchrotron enabled soft matter research: From polymers to nanocellulose

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.