RESUMO
MDOC comprises small, essentially insoluble, particles which associate to form "weak gel" networks at concentrations above â¼4wt%. 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 â¼60 to â¼1800kDa, we found that the concentration required to give maximum G' for 5wt% dispersions of MDOC increased systematically from â¼0.005wt% for the lowest molecular weight to â¼0.3wt% 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.