Cedar leaf-like bifunctional coating with excellent contact electrical conductivity and waterproofness

Abstract

Traditional electrically conductive coatings applied to the field of connectors would cause electrical signal crosstalk or even short circuits due to their excellent electrical conductivity. Meanwhile, the traditional waterproof coatings were difficult to achieve excellent electrical conductivity due to their high contact resistance. Therefore, there was a long-standing contradiction between electrical conductivity and waterproofing in the field of connectors. Based on the conductive effect of electronic tunnel, a new design concept of electrically conductive and waterproof coating was proposed. An ultra-thin and highly cross-linked hydrophobic coating was manufactured onto a dense electrically conductive coating so as to create a bifunctional coating. Simultaneously, the hydrophobic coating was thin enough so that it did not destroy the conductive response of electronic tunnel. Concretely, the electrically conductive coating (polyaniline) was in-situ polymerized on the substrate by plasma initiation, and then another ultra-thin hydrophobic coating (polysiloxane) was also polymerized onto the initial conductive coating by a similar method. The contact conductivity of the bifunctional coating was up to 2.08 × 107S/m. The plasma firstly initiated the dissociation of reactive monomers, and then polymerization. Consequently, these two monomers with different polarity (aniline and hexamethyldisiloxane) can sequentially polymerize to form a dense coating. Importantly, the interface between the conductive coating and hydrophobic coating were connected by chemical bond without delamination failure. Interestingly, the surface of the bifunctional coating exhibited a protrusion like structure of cedar leaves, resulting in the water contact angle to reach 133.3°. This work provided clear guidance and a strong impetus for the development of contact electrical conductivity and waterproofness for the connector field.