Thermoplastic arabinoxylan derivatives: A study of their structure and dynamics
Doktorsavhandling, 2025
The structure and dynamics of polymers at the molecular and nanometer scale controls how the material responds to stimuli such as heat and strain. To advance the development of polysaccharide-based thermoplastics require that we also further our understanding of their molecular scale properties and how these are altered by modification processes. This thesis aims to understand the mechanisms that allow for a flexible thermoplastic polysaccharide material to be produced via oxidation-reduction and etherification modification of arabinoxylan (AX). The effect of these modifications on the structure and dynamics of linear polysaccharides, such as cellulose and alginate, have been studied but with few experimental measurements of changes at the molecular scale. Characterization of modifications on branched polysaccharides such as AX are even more limited.
AX studied in this work, is a polysaccharide consisting of ß-(1→4)-D-xylopyranosyl repeating units partially substituted with α-L-arabinofuranosyl units, and is a major hemicellulose component in wheat bran. To understand the changes in structure, we utilize small and wide-angle X-ray scattering techniques to characterize solid films and water dispersions. To study the dynamics, we combine thermomechanical characterization, NMR and quasielastic neutron scattering techniques to obtain information across different timescales.
A higher degree of arabinose substitution in AX was correlated with a more extended chain conformation when dispersed in water, and the absence of ordered crystalline regions in the solid films. Oxidation-reduction that results in the ring-opening of the AX does not significantly alter the conformation in water, however, increased chain mobility was observed in the ring-opened solid materials, specifically at the modified positions of the carbohydrate ring. Etherification leads to nanoscale phase separation in the system's structure, and adds sub-glass transitions to the dynamics. Lastly, when combining oxidation-reduction with etherification, we observed synergistic effects from the mobility of the ring-opened AX chain and the additional motions provided by the side chains.
AX studied in this work, is a polysaccharide consisting of ß-(1→4)-D-xylopyranosyl repeating units partially substituted with α-L-arabinofuranosyl units, and is a major hemicellulose component in wheat bran. To understand the changes in structure, we utilize small and wide-angle X-ray scattering techniques to characterize solid films and water dispersions. To study the dynamics, we combine thermomechanical characterization, NMR and quasielastic neutron scattering techniques to obtain information across different timescales.
A higher degree of arabinose substitution in AX was correlated with a more extended chain conformation when dispersed in water, and the absence of ordered crystalline regions in the solid films. Oxidation-reduction that results in the ring-opening of the AX does not significantly alter the conformation in water, however, increased chain mobility was observed in the ring-opened solid materials, specifically at the modified positions of the carbohydrate ring. Etherification leads to nanoscale phase separation in the system's structure, and adds sub-glass transitions to the dynamics. Lastly, when combining oxidation-reduction with etherification, we observed synergistic effects from the mobility of the ring-opened AX chain and the additional motions provided by the side chains.
solid-state NMR
Polysaccharide
small-angle scattering
polymer conformation
hemicellulose
quasielastic neutron scattering
Vasa A, Vera Sandbergs Allé 8, Chalmers
Opponent: Dr. Laurent Heux, Director of Research, CERMAV-CNRS, France
Författare
Ratchawit Janewithayapun
Tillämpad kemi 3.3
Nanostructures of etherified arabinoxylans and the effect of arabinose content on material properties
Carbohydrate Polymers,;Vol. 331(2024)
Artikel i vetenskaplig tidskrift
Correlation between arabinose content and the conformation of arabinoxylan in water dispersions
Carbohydrate Polymers,;Vol. 368(2025)
Artikel i vetenskaplig tidskrift
R. Janewithayapun, H. Karlsson, M. S. Hedenqvist, D. W. Juhl, T. Vosegaard, L. Evenäs, A. Ström Dynamics of ring-opened arabinoxylan studied with solid-state NMR
R. Janewithayapun, H. Karlsson, F. Herranz-Trillo, A. E. Terry, L. Evenäs, F. Cousin, A. Ström Effect of periodate oxidation and borohydride reduction on the chemical structure and chain conformation of highly branched arabinoxylan
Achieving thermoplasticity in polysaccharides – being moldable under heat and pressure, is a challenging task. Trees, cereals and grasses will degrade and burn before they melt, and the same applies to polysaccharides extracted from them. Nonetheless, through chemical and other modification methods, examples of successful attempts have been demonstrated - materials such as those investigated in this work, which are almost impossible to distinguish from the plastic bag it is placed in. For these modified polysaccharides to truly serve as viable alternatives to fossil-fuel based plastics, however, one of many challenges to be addressed is achieving thermoplasticity with the minimum degree of modification required.
Answering this question requires us to understand what the different modifications do to the polysaccharide – how the molecular structure and behavior are altered throughout the modification route, so that we can begin to distinguish more and less efficient methods. With the starting point and the end point being known, this thesis aims to uncover the mechanisms occurring in the pathway from a brittle polysaccharide to a flexible thermoplastic material.
The polysaccharide studied in this work is arabinoxylan, a major hemicellulose component in wheat bran. As wheat bran is an agricultural side stream, arabinoxylan has the potential to be extracted in commercially viable amounts. More importantly, arabinoxylan is used here as a model system that is mostly amorphous, they do not contain ordered hierarchical structures like those found in cellulose. This means that arabinoxylan can be evaluated from the perspective of a simpler polymer chain. Two modification reactions were investigated, both independently and in combination. The first reaction aims at modifying the flexibility of arabinoxylan by causing a ring-opening. The second involves adding longer flexible side groups on the arabinoxylan to create an internally plasticized system. By means of various characterization techniques, this work shows correlation between changes in structure and dynamics on the smaller molecular level to bulk properties that determine the material behavior macroscopically.
Answering this question requires us to understand what the different modifications do to the polysaccharide – how the molecular structure and behavior are altered throughout the modification route, so that we can begin to distinguish more and less efficient methods. With the starting point and the end point being known, this thesis aims to uncover the mechanisms occurring in the pathway from a brittle polysaccharide to a flexible thermoplastic material.
The polysaccharide studied in this work is arabinoxylan, a major hemicellulose component in wheat bran. As wheat bran is an agricultural side stream, arabinoxylan has the potential to be extracted in commercially viable amounts. More importantly, arabinoxylan is used here as a model system that is mostly amorphous, they do not contain ordered hierarchical structures like those found in cellulose. This means that arabinoxylan can be evaluated from the perspective of a simpler polymer chain. Two modification reactions were investigated, both independently and in combination. The first reaction aims at modifying the flexibility of arabinoxylan by causing a ring-opening. The second involves adding longer flexible side groups on the arabinoxylan to create an internally plasticized system. By means of various characterization techniques, this work shows correlation between changes in structure and dynamics on the smaller molecular level to bulk properties that determine the material behavior macroscopically.
Fysikalkemiska koncept för utveckling av termoplastiska polysackarider
Formas (2020-01235), 2021-01-01 -- 2023-12-31.
Ämneskategorier (SSIF 2025)
Materialkemi
Polymerkemi
Infrastruktur
Chalmers materialanalyslaboratorium
DOI
10.63959/chalmers.dt/5773
ISBN
978-91-8103-316-8
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5773
Utgivare
Chalmers
Vasa A, Vera Sandbergs Allé 8, Chalmers
Opponent: Dr. Laurent Heux, Director of Research, CERMAV-CNRS, France
Relaterade dataset
Correlating side-chain and backbone dynamics of modified polysaccharide to glass transition temperatures: IN16b, OSIRIS [dataset]
DOI: https://doi.ill.fr/10.5291/ILL-DATA.9-11-2272, https://doi.org/10.5286/ISIS.E.RB2510196