Stretchable but superhydrophobic polymer thin film synthesis with conformal coverage and optical transparency

Abstract

Nano-scaled stretchable films with super-hydrophobicity have highly attractive poten-tial in the diverse application fields including waterproof and antifouling treatment of various stretchable micro-devices such as wearable electronics or functional textiles. Herein, nano-scaled uniform and stretchable polymer films providing sufficient hydrophobic performance were pre-pared by initiated chemical vapor deposition (iCVD) without utilizing micro- or nano- topogra-phy. The novel properties of polymer films integrating superhydrophobicity and high stretchabil-ity were achieved through the copolymerization of two monomers of 1H,1H,2H,2H-perfluorooctyl acrylate (PFOA) and 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane (V3D3) to form a crosslinked fluoropolymer network with low crystallinity and elasticity as well as the outstand-ing hydrophobicity. The composition of copolymers was adjusted by controlling the flow rates of the monomers, PFOA and V3D3, and confirmed through FT-IR and TOF-SIMS. The copolymer film with the optimized composition showed the elastic limit higher than 200% while maintain-ing the superhydrophobic property. An 800 nm-thick copolymer thin film showed excellent me-chanical durability without any damage even in repeated tensile test. The elastic copolymer film also displayed excellent chemical resistance on various organic solvents for 24 hrs. The high transparency and high uniformity could enable this thin film to be successfully applied as sub-strates for displays. Thus, we believe this thin film can be widely applicable to superhydrophobic modification of various stretchable nano- and micro devices such as wearable electronic device, due to its conformal deposition with easy control of nano-scale thickness.