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 M ¯ . 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 η o ∝ c 3.0M ¯ 6.6 . However, when PBIC was dissolved in benzene the l p was greatly reduced and the scaling law now was η o ∝ M ¯ 4.2 , 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 η o ∝ c 2.5M ¯ 3.5 . 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.