Thesis

From molecular-ion interactions to gel properties : a combined computational–experimental investigation of alginates

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Awarding institution
  • University of Strathclyde
Date of award
  • 2026
Thesis identifier
  • T17650
Person Identifier (Local)
  • 202183514
Qualification Level
Qualification Name
Department, School or Faculty
Abstract
  • Sodium alginate is a sustainable polymer that gels on contact with calcium ions. Alginate is a polysaccharide composed of two monomers: α-L-guluronate (G) and β-Dmannuronate (M). The aim of this thesis is to investigate the impact of monomer type and cation environment on alginate behaviour. Molecular dynamics was used to investigate the effects of these factors on alginate trimers in solution. G trimers formed more buckled structures than M, as evidenced by the 5-8 % increase in end-to-end distances. These values decreased in systems with calcium ions by as much as 3 %. In systems with calcium ions, mixing of G and M trimers resulted in a 550 % increase in trimer clustering compared to pure G or M systems, as shown by the number and size of clusters that formed. To extend this work, the G:M ratio and cation environment were examined experimentally. A design of experiments study investigated the effects of different curing conditions on calcium alginate gel strength. Introduction of excess sodium ions had a significant (p<0.05) effect on calcium alginate gel strength, inducing an average decrease of 30.7 %. To examine this effect further, molecular dynamics was used to compare 24-monomer G and M chains in stoichiometric and excess sodium ion environments. Analysis of the radius of gyration and chain-chain radial distribution functions showed that an increase in sodium ion concentration created more open G structures with more G-G interaction and more closed M structures with less M-M interactions. Systems with low sodium ion content presented with more favourable G-M interactions, compared with G-G or M-M, as shown in the distribution functions. This work has shown that excess sodium ion content and blended G/M polymer interactions, which have previously been overlooked in alginate research, contribute extensively to sodium and calcium alginate properties.
Advisor / supervisor
  • Johnston, Karen
  • Mulheran Paul A
Resource Type
DOI
Date Created
  • 2025

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