Phase behavior and dynamics of Pluronic®-based additives in semidilute solutions of poly(ethersulfone) and poly(N-vinyl pyrrolidone): rheological and dynamic light scattering experiments
AbstractThe phase behavior and dynamical properties of a pristine Pluronic® F127 and a Pluronic®-based multiblock copolymer, respectively, in semidilute solutions of poly(ethersulfone) (PESU) and poly(N-vinyl pyrrolidone) (PVP) in N-methyl-2-pyrrolidone (NMP) are investigated using shear rheological and dynamic light scattering (DLS) experiments. Pluronic® F127 is used for synthesis of the PESU-based multiblock copolymer. If the concentration of this additive exceeds a critical value, the solutions are characterized by a pronounced elasticity because of the phase behavior of the solutions, i.e., the polymer solution with three polymeric components depicts a miscibility gap which is associated with an interfacial tension in the two-phase regime. The addition of pristine Pluronic® F127 or the Pluronic®-based multiblock copolymer leads to an additional relaxation process. The zero shear rate viscosity data are qualitatively reproduced by the Palierne model. Phase separation above the critical concentration is supported by a relatively low diffusion coefficient as determined by DLS experiments.