Durable, superoleophobic polymer-nanoparticle composite surfaces with re-entrant geometry via solvent-induced phase transformation.

Philip S Brown,Bharat Bhushan

doi:10.1038/srep21048

Abstract

Superoleophobic plastic surfaces are useful in a wide variety of applications including anti-fouling, self-cleaning, anti-smudge, and low-drag. Existing examples of superoleophobic surfaces typically rely on poorly adhered coatings or delicate surface structures, resulting in poor mechanical durability. Here, we report a facile method for creating re-entrant geometries desirable for superoleophobicity via entrapment of nanoparticles in polycarbonate surfaces. Nanoparticle incorporation occurs during solvent-induced swelling and subsequent crystallization of the polymer surface. The resulting surface was found to comprise of re-entrant structures, a result of the nanoparticle agglomerates acting as nucleation points for polymer crystallization. Examples of such surfaces were further functionalized with fluorosilane to result in a durable, super-repellent surface. This method of impregnating nanoparticles into polymer surfaces could prove useful in improving the anti-bacterial, mechanical, and liquid-repellent properties of plastic devices.

Highlights

Designed to minimize the liquid-solid contact fraction to ensure the droplet is resting mostly on air pockets for the surface to be repellent
The structures need to be as thin as possible[7]. Such surface features are fragile and difficult to fabricate on a large scale and singly re-entrant geometries are more commonly used in liquid repellency
Several use a “one-pot” technique with all materials mixed and deposited together[10,11]. Such techniques typically suffer from poor durability due to the weak interfacial adhesion between the substrate and the low surface tension material required for oil repellency

Summary

Introduction

Designed to minimize the liquid-solid contact fraction to ensure the droplet is resting mostly on air pockets for the surface to be repellent. Many existing methods for creating superoleophobic surfaces rely on coatings to add roughness and low surface tension material to a substrate[3,4]. Nanoobjects can be dispersed in a monomer, which is polymerized in situ, allowing for better dispersion of the nanomaterial and less agglomeration, this technique relies on the use of organic solvents and is less compatible with common industrial processes such as extrusion[17] Another method to add nanoparticles is to use supercritical CO2 to impregnate the polymer[18], this requires the use of high-pressure equipment[19] and results in nanoparticles being impregnated throughout the plastic, affecting the properties of the bulk. For liquid repellency, it is desirable for the nanoparticle agglomerates to be present at the interface to provide the re-entrant geometry required

Methods

Results

Conclusion