Abstract
The wettability of poly (dimethylsiloxane) (PDMS) coating on plasma-treated glass was studied at room temperature using polar and non-polar liquids. The wettability was investigated regarding the liquids’ surface tensions (STs), dielectric constants (DCs) and solubility parameters (SPs). For polar liquids, the contact angle (CA) and contact angle hysteresis (CAH) are controlled by the DCs and non-polar liquids by the liquids’ STs. Solubility parameter difference between the PDMS and the liquids demonstrated that non-polar liquids possessed lower CAH. An empirical model that integrates the interfacial properties of liquid/PDMS has been composed. Accordingly, the difference between the SPs of PDMS and the liquid is the decisive factor affecting CAH, followed by the differences in DCs and STs. Moreover, the interaction between the DCs and the SPs is of importance to minimize CAH. It has been concluded that CAH, and not CA, is the decisive attribute for liquid repellency of PDMS coating.
Highlights
Super-repellent surfaces capable of repelling both polar and non-polar liquids have stimulated considerable interest due to their importance in various industrial applications such as antifogging, anti-icing, inks, oil/water separation, etc [1,2,3]
The results demonstrate a good correlation between the liquids properties and the all liquids exhibit the general tendency to decrease liquids’ surface tension with reduced static Contact angle (CA), wettability
The relationship between the CA hysteresis (CAH) and the square root of the combined square power of the solubility parameter and the surface tension for the non-polar liquids exhibits a lower CAH than for the polar liquids. This may be attributed to the influence of the solubility parameter on the CAH that is associated with the actual contact of the liquid with the surface
Summary
Super-repellent surfaces capable of repelling both polar and non-polar liquids have stimulated considerable interest due to their importance in various industrial applications such as antifogging, anti-icing, inks, oil/water separation, etc [1,2,3]. When the surface brushes are in contact with non-polar liquids (alkanes), which are considered good solvents for PDMS, a “blended liquid–liquid interface” is achieved This unique interfacial phenomenon is characterized by the ability of the PDMS brushes to interact and be swollen by the non-polar liquids, leading to an increase in the brushes’ mobility and enhancing the liquid-like behavior of the PDMS coating. Urata et al [8] studied the molecular conformation of surface-tethered alkyl groups interacting with a variety of probe liquids and their wettability by measuring the static and dynamic contact angles They demonstrated that a good correlation exists between the CAH and the dielectric constants of the probe liquids. This study consists of a comprehensive analysis of the interfacial wetting dynamics between PDMS coating and a variety of polar and non-polar liquids considering their surface tension, dielectric constant, and solubility parameters
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