Entanglement effects in semiflexible polymer solutions. 2. Huggins coefficient and inclusion of intermolecular hydrodynamic interactions

A previously proposed viscosity equation for stiff-chain polymer solutions based on the fuzzy cylinder model theory was modified by incorporating empirically the effect of intermolecular hydrodynamic interaction (HI). The Huggins coefficient k' derived from the modified viscosity equation consists of the contributions of the entanglement interaction (k'(EI)) and of the intermolecular HI (k'(HI)). While the former can be calculated using the fuzzy cylinder model theory, the latter remains as an adjustable parameter. For various stiff-chain polymer solutions, k'(HI) was estimated by subtracting the calculated k'(EI) from experimental k'. The results for dichloromethane (DCM) solutions of poly(n-hexyl isocyanate) (PHIC) showed that k'(HI) is much smaller than k'(EI) at 1 less than or equal to N less than or equal to 10, where N is the number of Kuhn's statistical segments per molecule, but becomes important outside the above N range. Zero-shear viscosities calculated by the modified viscosity equation for concentrated DCM solutions of PHIC were favorably compared with experimental data for N up to 15.