Synthesis of a Stretchable but Superhydrophobic Polymer Thin Film with Conformal Coverage and Optical Transparency

Abstract

An elastic film with water repellency is of great interest for application to waterproof and antifouling surface treatment of stretchable devices such as wearable electronics or functional textiles. Herein, a nanoscale ultrathin stretchable polymer film endowed with superhydrophobicity was newly designed and synthesized by a vapor phase method, initiated chemical vapor deposition (iCVD). The highly stretchable superhydrophobic polymer film was generated from the copolymerization of 1H,1H,2H,2H-perfluorooctyl acrylate (PFOA) and 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane (V3D3) to form a cross-linked fluoropolymer network with low crystallinity and elasticity as well as superhydrophobicity. The composition of the copolymer film was adjusted by controlling the flow rates of the input monomers of PFOA and V3D3 during the deposition process. The copolymer film with the optimized composition showed an elastic limit higher than 200% while maintaining the superhydrophobic property with a water contact angle greater than 150°on nonflat substrates. An 800-nm-thick copolymer thin film showed mechanical durability with superhydrophobic performance even after 2000 cycles of a 200% stretch test. The elastic copolymer film also displayed solvent resistance against incubation in various organic solvents for 24 h. Transparency greater than 90% was also confirmed in the whole visible range with large-area uniformity and conformal coverage. We believe the stretchable superhydrophobic polymer film developed in this study is a promising candidate material for passivation of various stretchable device applications.

Initiated Chemical Vapor Deposition (iCVD) of Bio-Based Poly(tulipalin A) Coatings: Structure and Material Properties

“…It was done by recording and plotting the wavelength versus light transmittance. This method was previously used for thin films on substrates to prove their transparency [ 43 , 44 ]. The characterization was performed using polycarbonate ( Figure 6 a) since it is an amorphous thermoplastic, as well as by using microscopic glass substrates ( Figure 6 b).…”

A Fully Transparent, Stretchable Multi‐Layered Water Barrier Thin Film for the Passivation of Underwater Device Applications

“…The elastic limit of the three‐layered pV100‐FV was found to be about 60%, confirmed by the cyclic stress–strain curves (Figure 3a, inset). This value is lower than that of the pristine pFV layer (120% elastic limit), [ 10 ] mainly due to the addition of highly crosslinked, rigid pV4D4 in the pFV layer. However, despite the reduced elongation limit, the stretchability of the pV100‐FV barrier coating shown this work is sufficient for various embeddable and wearable device applications.…”

“…Reducing the free volume of an elastomer without sacrificing its stretchability is the key to develop a stretchable water barrier coating with low permeability. Although we have demonstrated a superhydrophobic elastomer coating with excellent stretchability previously, [ 10 ] its large free volume stemming from the long fluoroalkyl chain in the superhydrophobic elastomer resulted in the increase in the water permeability as well. Here we aim to reduce the large free volume of the superhydrophobic coating (pFV) without compromising its excellent stretchability by sequentially depositing pV4D4, a highly crosslinked organosilicone polymer ( Figure a).…”

“…Recently, we reported a new type of stretchable superhydrophobic elastomer coating composed of a copolymer of a fluoroalkyl monomer and an organosiloxane crosslinker, synthesized in vapor phase via initiated chemical vapor deposition (iCVD). [ 10 ] The solvent‐free process can deposit various functional polymer coatings on target substrates in damage‐free way, and enables precise control of film thickness down to nanometer scale. [ 10,11 ] However, just as most elastomers, the copolymer film was also permeable to water vapor mainly due to the high free volume in its structure.…”

“…[ 10 ] The solvent‐free process can deposit various functional polymer coatings on target substrates in damage‐free way, and enables precise control of film thickness down to nanometer scale. [ 10,11 ] However, just as most elastomers, the copolymer film was also permeable to water vapor mainly due to the high free volume in its structure. In this work, we demonstrate a new architecture of highly stretchable water barrier coating with improved water barrier property by depositing alternating layers of the stretchable, superhydrophobic copolymer film and a heavily crosslinked organosiloxane polymer.…”