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Restriction lift date:2018-04-21
Citation:Xie, X., Agoub, A. A. and Morris, E. R. (2017) 'Effect of molecular weight on the ability of guar gum to enhance “weak gel” rheology of microdispersed oxidised cellulose (MDOC)', Carbohydrate Polymers, 169, pp. 393-397. doi: 10.1016/j.carbpol.2017.04.039
MDOC comprises small, essentially insoluble, particles which associate to form “weak gel” networks at concentrations above ∼4 wt%. Association is promoted by guar gum, causing an increase in G′ at low levels of addition and a decrease at higher concentrations, due to excessive aggregation of the MDOC particles. For guar gum samples with molecular weights ranging from ∼60 to ∼1800 kDa, we found that the concentration required to give maximum G′ for 5 wt% dispersions of MDOC increased systematically from ∼0.005 wt% for the lowest molecular weight to ∼0.3 wt% for the highest. We propose that guar gum drives self-association of MDOC to reduce enthalpically-unfavourable (segregative) interactions between the two materials, and that large coils are less effective than smaller ones because a higher proportion of chain sequences are buried in the interior of the coil, where they cannot make segmental contacts with the MDOC particles.
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