Dynamics of a semiflexible polymer poly(n‐hexyl isocyanate) in isotropic solution. 1. Zero shear viscosity

Abstract

Zero shear viscosities η0 were measured for toluene solutions of ten fractionated poly(n‐hexyl isocyanate) (PHIC) samples from dilute regime to concentrated isotropic regime. PHIC is a semiflexible polymer with the persistance length q=37 nm in toluene. For six PHIC samples with the molecular weight less than 14×104, the dependence of η0 on the polymer concentration c did not obey any power law, while for the higher molecular weight samples, n0 was almost proportional to c3.2 in a high c region. At fixed c, η0 was almost proportional to M4v in a high Mv region (Mv: viscosity average molecular weight). These concentration and molecular weight dependences are distinct from not only those for flexible polymer solutions but also those for much stiffer polymer solutions [e.g., schizophyllan (q=200 nm) and xanthan (q=120 nm)]. The results of η0 for PHIC solutions obtained were compared with Teraoka–Hayakawa’s theory for rodlike polymer solutions and with our fuzzy cylinder model theory for semiflexible polymer solutions. The former theory agreed with the experimental results only for the second lowest molecular weight sample with a rodlike conformation. On the other hand, the latter theory succeeded in explaining quantitatively the results for seven samples with intermediate molecular weights. Neither of the theories agree with the data for the lowest molecular weight sample, because they neglected the intermolecular hydrodynamic interaction which becomes important for short chain polymers. For the two highest molecular weight samples, the fuzzy cylinder model theory failed to describe the η0 data, because of some additional flexibility effect which is not cleared yet.