More fluorous surface modifier makes it less oleophobic: fluorinated siloxane copolymer/PDMS coatings

Area of Science:

• Materials Science
• Surface Chemistry
• Polymer Science

Background:

• Polydimethylsiloxane (PDMS) coatings are widely used but can be modified to enhance specific surface properties.
• Copolyacrylates with semifluorinated and polydimethylsiloxane side chains offer tunable surface characteristics.

Purpose of the Study:

• To investigate the effect of a specific copolyacrylate (D5-3) as a surface modifier on PDMS coatings.
• To understand the relationship between D5-3 concentration and the wetting behavior (oleophobicity) of PDMS surfaces.
• To elucidate the underlying mechanisms of surface property changes with D5-3 concentration.

Main Methods:

• Dynamic contact angle (DCA) analysis using isopropanol to assess wetting behavior.
• Dynamic light scattering (DLS) studies on a model PDMS/D5-3 system to investigate aggregation.
• Scanning electron microscopy (SEM) and atomic force microscopy (AFM) to analyze bulk morphologies.

Main Results:

• A maximum in surface oleophobicity was observed at 0.4 wt% D5-3 concentration.
• Increased D5-3 concentrations (>0.4 wt%) led to decreased oleophobicity, indicated by lower contact angles.
• DLS studies revealed D5-3 aggregation is dependent on temperature and concentration, suggesting a critical micelle concentration (cmc) around 0.4 wt%.
• SEM and AFM confirmed increased aggregate formation at D5-3 concentrations above 0.4 wt%.

Conclusions:

• The optimal surface concentration for enhanced oleophobicity of PDMS using D5-3 is approximately 0.4 wt%.
• Above this concentration, D5-3 undergoes phase separation and aggregation, leading to reduced surface oleophobicity.
• The findings provide insights into the self-assembly behavior of amphiphilic copolymers at interfaces and their impact on surface properties.