Dynamic Segment Size of the Cellulose Chain in an Ionic Liquid

Abstract

Viscoelasticity and strain-induced birefringence under oscillatory shear flow of cellulose/1-buthyl-3-methylimidazolium chloride (BmimCl) solutions were measured at various temperatures covering a wide frequency zone from the terminal flow to the glassy zone for dilute (2 wt %) and semiconcentrated solution (10 wt %) to clarify the dynamical segment size of the cellulose chain. The estimated dynamical segment size, MS, obtained from viscoelasticity is much smaller than that from flow birefringence. MS estimated from dynamic birefringence was 2300 corresponding to 14 repeating glucose residues from 2–10 wt %, showing weak concentration dependence. This value is comparable to the reported value of Kuhn segment size, MK. This relationship, MS ≈ MK, holding even at dilute solution, is in contrast with the large difference (MS ≈ 5MK) for polystyrene in dilute solution, indicating that the chain rigidity affects the relationship between MS and MK.