Shear rheology and scaling of semiflexible polymers: Effect of polymer-solvent interactions in the semidilute regime

Semiflexible polymers and their assemblies are important in biology as cross-linked networks of semiflexible polymers form a major structural component of tissue and living cells. This research used shear rheology to demonstrate the tuning from worm-like to rod-like conformation in semiflexible polymers by polymer-solvent interactions. The conformation was assessed by the persistence length l_p, and its influence, in the semidilute regime, was assessed by the scaling of zero-shear viscosity η_o with concentration c and molecular weight . The polymers were poly n-butyl and poly n-octyl isocyanate (PBIC and POIC, respectively). PBIC exhibited the largest l_p in chlorinated solvents, and the solutions obeyed the scaling law . However, when PBIC was dissolved in benzene the l_p was greatly reduced and the scaling law now was , consistent with a worm-like conformation. On the other hand, POIC dissolved in chlorinated and benzenic solvents exhibited a worm-like conformation and the scaling was . These results were contrasted with those of hydroxypropyl cellulose (HPC) aqueous solutions, which exhibit worm-like conformation, the solutions obeyed the scaling η_o ∝ c^2.5 . Finally, the shear viscosity of the polyisocyanates and HPC obeyed the Saito scaling, valid for anisotropic particles in solution.