Characterization of nanoscale pinhole defects in hydrophobic coatings using copper electrodeposition

Abstract

Thin (∼ 100 nm thick) hydrophobic polymer films are used in a plethora of applications where water repellency is required. However, hydrophobic film implementation in industry is limited due to poor durability. Thin hydrophobic film blistering during condensation has been identified as one of the main mechanisms associated with failure. Yet, disagreement exists about the source of blister initiation. Furthermore, there is a lack of understanding about the physical defects or pinholes that facilitate vapor penetration pathways through thin hydrophobic films. These pinholes govern the nucleation of blisters on the interface between the hydrophobic polymer and metal substrate. Here, we use metal electrodeposition as a means to characterize these intrinsic pinholes in thin hydrophobic polymers. A facile method is demonstrated to locate pinholes and measure pinhole density on CFx and poly(2-chloro-p-xylylene) (Parylene C) films. Our work not only helps to understand the intrinsic defects associated with film deposition, it also provides design guidelines for the selection and development of efficient thin film hydrophobic coatings.