Aqueous/brine solutions viscosity and surface properties of hydrophobically modified scleroglucans: Role of grafted chain length

Acyl chlorides with different alkyl lengths (C6, C10 or C18) are grafted onto scleroglucan (Sclg) and aqueous/brine solutions viscosities of modified samples are studied at 25/90 °C. All modified Sclgs solutions show lower viscosities than those of the unmodified Sclg solutions, due to the helix-coil transition caused by the modification. The viscosity of the samples aqueous solutions at 25 °C is increased by increasing the grafted alkyl length. However, the viscosity profiles of the aqueous solutions of modified Sclgs are superimposable at 90 °C. The modified Sclg by C10 moieties exhibits the highest viscosity in the brine solution at 90 °C. The results are interpreted by a model depicting the effects of the alkyl lengths on the distances among the Sclg chains and the chains hydrophobic associations. Moreover, the surface and amphiphilic properties of the modified Sclgs in their aqueous solutions are correlated with their alkyl side chain length.