Blocking the Intercalation of Cyclic Poly(ethylene oxide)s into Graphite Oxide for Separation Performance

Significance 

Macrocyclic polymers (polymers having more than 20 atoms in a ring structure), have been the center of research attraction, particularly over the last decade. Much of this interest can be attributed to unique physical properties: such as reduced melt viscosity, reduced entanglement and increased glass transition temperature at medium-low molecular weight, most of which can be traced to the absence of end groups in their topologies. Advances in this field have led to the development of graphite oxide-based materials. Technically, graphite oxide is a layered material derived from graphite and is basically composed of carbon, oxygen, and hydrogen. To date, the structural composition of graphite oxide has remained a contentious issue amongst various scientists and scholars. Existing literature reports of two feasible models for establishing the structural composition of graphite oxide; both of which still call for further improvement.

Essentially, in these types of models, one ought to understand the type of interactions between the graphite oxide functional groups and intercalant species. On this basis, scientists from the Materials Physics Center in Spain: Professor Fabienne Barroso-Bujans and Professor Angel Alegria, in collaboration with Professor Jürgen Allgaier at the Jülich Centre for Neutron Science and Institute for Complex Systems, Forschungszentrum Jülich GmbH, in Germany investigated the intercalation kinetics of cyclic poly(ethylene oxide) (CPEO) into graphite oxide from the melt and of their linear PEO (LPEO) analogues. Their motivation was based on the background knowledge on the cyclic topology influence on many physical properties of polymers. Their work is currently published in the research journal, Macromolecules.

In their approach, the research team performed kinetic measurements of the melt intercalation of CPEO and LPEO by monitoring the reduction of melting peak areas of PEO after the isothermal annealing of mixtures of PEO and graphite oxide-based structures at 80 °C and the subsequent cooling of samples on a DSC capsule. This experimental approach is based on the suppression of polymer thermal transitions (crystallization and melting) that the intercalated polymer phase experiences under extreme two-dimensional confinement.

The authors reported that the intercalation rate was faster for LPEO than for CPEO, although the differences were not big. More so, the team demonstrated that by pillaring the graphite oxide structure with 1 wt % of 1,6-hexanediamine, the topological sensitivity of the intercalation of CPEO and LPEO was dramatically enhanced. Remarkably, their results were supported by complimentary X-ray diffraction (XRD) and time-resolved Fourier transform infrared (FTIR) spectroscopy data.

In summary, the study assessed the role of poly (ethylene oxide) (PEO) topology in the melt intercalation in graphite oxide- based materials. Their results suggested that it is possible to restrict the intercalation of cyclic PEO into partially pillared graphite oxide, whilst allowing the linear analogue to diffuse through the graphite oxide interlayer space. In a statement to Advances in Engineering, Professor Professor Fabienne Barroso-Bujans emphasized that the aforementioned finding could potentially be the basis for developing new methods of purification of cyclic polymers.

Blocking the Intercalation of Cyclic Poly(ethylene oxide)s into Graphite Oxide for Separation Performance - Advances in Engineering

About the author

Fabienne Barroso-Bujans is an IKERBASQUE Reseach Professor at the Donostia International Physics Center, in Donostia-San Sebastian, Spain. She studied chemistry at the University of Havana, Cuba, and received her PhD from the University of Chile in 2004 under a German DAAD program. Her research interests include polymer synthesis with complex structures (e.g. macrocyclic polymers), the synthesis of 2D confined spaces for the study of problems related to polymers under confinement and molecular sieving, and the study of structure-property relationships of materials based on polymers.

About the author

Jürgen Allgaier studied chemistry at the University of Freiburg and obtained his doctorate in 1993. He worked in Strasbourg at the Institut Charles Sadron and as Postdoctoral Fellow at Sheffield University on research projects in anionic polymerization. In 1995 he joined the Forschungszentrum Jülich. At the Jülich Centre for Neutron Science his present research interests are in the areas of anionic polymerization, polymers with architecture and cyclic polymers. Further research fields include supramolecular polymers, polymer-particle composites and polymer-lipid interactions a s well as the development of deuteration techniques for polymers and organic compounds. In 2002 he was awarded the Erwin Schrödinger-Prize for Interdisciplinary Research.

About the author

Angel Alegría is a full Professor at the University of the Basque Country and a member of the Material Physics Center (CSIC-UPV/EHU). Dielectric relaxation techniques are the main experimental tools used in his research in combination with other complementary experimental methods.

His research interest focuses on the dynamics of polymers and soft matter: dynamical processes ranging from the very local intramolecular motions to the large-scale dynamics, with emphasis in the cooperative segmental relaxation associated to the glass transition.

Reference

F. Barroso-Bujans, J. Allgaier, A. Alegria. Poly (ethylene oxide) Melt Intercalation in Graphite Oxide: Sensitivity to Topology, Cyclic versus Linear Chains. Macromolecules 2020, volume 53, page 406−416.

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