Molecular Weight Dependence of Surface Tension of Poly(ethylene oxide) Solution

Surface tension plays a critical role in a wide range of fields such as adhesion, wetting, and capillarity. Herein, we combine experiments and molecular dynamics (MD) simulations to study the surface tension (γ) of poly(ethylene oxide) (PEO) solution as a function of its molecular weight (M). In experiments, we reveal that γ is scaled to M with |γ - γ_∞| ∝ M^α up to a critical molecular weight (M*). Simulation with a coarse-grained polymer solution model shows that α decreases as the solvent quality becomes worse. The combination of the experiments and simulations reveal that α is slightly affected by PEO concentration. On the other hand, M* decreases as the solvent quality decreases or as the polymer concentration increases. Our study demonstrates that the surface tension of the polymer solution is determined by the adsorption of the polymer at the air-solution surface.