Air entrainment dynamics of aqueous polymeric droplets from dilute to semidilute unentangled regimes

Abstract

Recent studies have revealed the air-cushioning effect of droplet impact upon various surfaces and although pure water droplets have been studied extensively, the air entrainment dynamics for aqueous polymeric droplets is the focus of this study. Herein, we show that for low to moderate Weber numbers, We ~ O(1 - 10), the air film thickness gradient is strongly influenced by the viscoelastic properties of the aqueous polymeric droplets in the dilute to the semidilute unentangled regimes. Droplets of aqueous polyethylene oxide (PEO) impacting a smooth thin oil film surface formed a submicron air layer moments prior to impact, which was tracked by a high-speed total internal reflection microscopy (TIRM) technique. The radial changes in the air film thickness were related to the polymer concentration, thus providing an alternative tool for comparing the rheometer-derived overlap concentrations with a contactless optical technique.

Total internal reflection microscopy: a powerful tool for exploring interactions and dynamics near interfaces

“…5B, He et al further studied the air entrainment dynamics of the polymeric droplets from dilute to semidilute unentangled regimes, indicating that a submicron air layer, whose thickness was related to the polymer concentration, could be formed before the droplet impacted the air-oil interface. 64 4.2.2 Interactions near polymer-grafted interfaces. The use of TIRM to study surface-grafted polymers is another topical research hotspot.…”