Solvent concentration in a specified region of regenerated cellulose solid evaluated from dynamic viscoelasticity in a hydrophilic solvent

An attempt was made to evaluate the solvent concentration nu in a specified amorphous region by the use of semi-empirical equation nu = (1 - T-fc/T-f)/(2T(fc)/T-m(s) - T-fc/T-f) where T-fc and T-f are peak temperatures of a dynamic loss tangent tan delta of a given dynamic absorption in solvent and dry air, respectively, and T-m(s) is the melting point of the solvent. A polymer blend with polystyrene and polymethylmethacrylate was used to confirm the reliability of the equation. The well-characterized two cuprammonium regenerated cellulose fibers, which were composed of the primary particles having ca. 15 nm in size, were used. More than 20 solvents with -OH groups were selected as an immersing media in order to clarify the diffusibility of a solvent into an amorphous region. The isochronal viscoelasticity in a solvent was measured. The results were: (1) the reliability of the equation was confirmed; (2) the nu value of the region relating to the dynamic absorption observed at higher temperature was smaller than that at lower temperature; (3) as for the interfacial region of the primary particle, nu ranged between 0.05 and 0.30 and varied depending on the chemical structure of a solvent. The nu value increased with a decrease in a molecular weight MW of the solvent and showed a minimum value at the solvent, which showed the critical balance between hydrophilic and lipophilic properties; (4) as for the inside of the primary particle, nu ranged between 0 and 0.21 and decreased with an increase in MW. With an increase in the number of OH groups in a solvent, nu increased. We concluded that the solvent diffused into a specific amorphous region depending on its affinity to cellulose molecule and the molecular size and the nu value was evaluated through the peak temperature of tan delta measured in the solvent. (C) 2000 Elsevier Science Ltd. All rights reserved.