Fluorescence depolarization and contact angle investigation of dynamic and static interfacial tension of liquid crystal display materials

Observation of wall wettability under imposed flow by fluorescence depolarization: dependence on surface oxygen content and degree of polymer branching

“…Γ SL has been determined for many decades under static or slow-flow conditions by sessile drop contact angle (θ c ) measurements [3]. It is known that θ c depends on surface roughness [3], on the chemical composition of both the solid surface and the flowing liquid [4][5][6], and on the relative orientation of the surface chemical groups [7]. Extrand [8] proposed a simple thermodynamic model for free energies of wetting obtained from the contact angles of small sessile drops spread on a solid surface and found reasonable agreement with bond strengths measured by other experimental methods.…”

“…Fluorescent depolarization of rhodamine in free-flowing films (FFF) generated by a liquid lobed jet [9] impinging on a nearly vertical solid surface has proved to be sensitive to different chemical constitutions of both the surface [10] and the flowing liquid [11], as well as the orientation of surface hydroxyls [7].…”

Detection of chemical alterations at internal walls of microchannel flow cells by nondestructive fluorescence depolarization

“…Static Γ SL have been determined for several decades by sessile drop contact angle (θ c ) measurements [2]. There is a causal relation between the advancing θ c and receding θ c and the interfacial chemical groups present at the interface, as well as their relative orientation [3,4].…”

Observation of the Effect of Wetting Efficiency on a Flow of Liquids Impinging on Solid Substrates by Fluorescence Depolarization

“…[2][3][4] Recently, two different coexisting contact angles were observed for the same drop on a rubbed polymer and attributed to spatial asymmetry of interfacial chemical interactions. 5 Studies of drops moving at quite low velocity on solid surfaces showed that hysteresis (difference between the advancing and the receding θ c ) has a strong dependence on sorption 2 and arises primarily from molecular interactions between liquid and solid rather than surface roughness. 3 It is known that an increase in the flow rate intensifies molecular effects compared to hydrodynamic effects, 1 increasing the contribution of chemical constitution and rendering chemical phenomena relevant.…”

“…These interactions depend on solid surface structure and roughness, 1 as well as on chemical constitution of the solid substrate 6 and the flowing liquid film. 7 Steady-state fluorescence depolarization was recently applied [5][6][7] to study interfacial molecular interaction of fast flowing thin liquid films, flowing without boundaries, on solid substrates. It was found that flows on borosilicate could be differentiated from those on tin dioxide, 6 as well as from those of liquid films with two different dissolved tensoactive substances flowing on the same substrate.…”