Elaboration of Voltage and Ion Exchange Stimuli-Responsive Conducting Polymers with Selective Switchable Liquid-Repellency

Abstract

In this work, we report the possibility to selectively switch by voltage and anion exchange the water-repellent properties, in comparison with the oil-repellent properties, of copolymers containing both fluorinated chain (EDOT-F8) and pyridinium (EDOT-Py(+)) moieties. Here, the fluorinated chains are necessary to reach superhydrophobic properties while the pyridinium moieties allow the switching in the wettability by counterion exchange. Because, conducting polymers can exist in their oxidized and reduced state, here, we report also the switching of their wettability by voltage. The best properties (superhydrophobic properties with low hysteresis and sliding and good oleophobic properties) are obtained for a % of EDOT-Py(+) of 25 %. Surprisingly, by reducing the polymer by changing the voltage, a selective decrease in the contact angle of water is observed, whereas that of oils (diiodomethane and hexadecane) remain unchanged, making it possible to have higher contact angles with diiodomethane than with water. Here, the switching in the wettability is due to the change of the water droplet from the Cassie-Baxter state to the Wenzel state by changing the voltage. Because of the presence of highly polar pyridinium groups and their perchlorate counterions, the wettability of oil droplets (diiodomethane and hexadecane) is not significantly affected. This effect is confirmed by changing the counterions with highly hydrophobic ones (C8F17SO3(-), Tf2N(-), or BF4(-)). Such materials are excellent candidates for oil/water separation membranes.

Highly Polar Linkers (Urea, Carbamate, Thiocarbamate) for Superoleophobic/Superhydrophobic or Oleophobic/Hydrophilic Properties

“…Surprisingly, it is also possible to have oil contact angles higher than water contact angles using urea linkers (NHCONH), which is rare in the literature. [27][28][29][30][31][32][33][34][35] In all the examples reported in the literature, there is the presence of both highly oleophobic parts such as fl uorinated materials and highly hydrophilic parts such as charged or highly polar species. For example, the group of Zhang reported the preparation of superhydrophilic/superoleophobic (in air) by mixing poly(diallyldimethylammonium chloride) (PDDA) with sodium perfl uorooctanoate (PFO).…”

“…[ 28 ] Otherwise, hydrophilic/ oleophobic properties were also reported by copolymerization of polymers containing fl uorinated chains and pyridinium groups. [ 32 ] Here, this possibility can be explained by the presence of both oleophobic fl uorinated chains and the most hydrophilic urea linkers (NHCONH). Using C 8 F 17 chains only a small difference between θ diiodomethane or θ sunfl ower oil is observed (for Q s = 200 mC cm −2 ) while this difference increases as the fl uorinated chain.…”

“…Here, we show also that some of these monomers can lead to both hydrophilic and oleophobic properties. This unusual surface property is rare in the literature [27][28][29][30][31][32][33][34][35] but possible by combining hydrophilic and oleophobic materials, and can found other applications in oil/water separation, [36][37][38] for example.…”

Switchable and Reversible Superhydrophobic Surfaces: Part Two

“…In order to reach superhydrophobic properties, PEDOT copolymers with both ion exchange functional groups and fluorinated chains were prepared by electro-copolymerization (Figure 19) [104,106]. The authors studied the influence of the percentage of each monomer, the doping state and also the counter-ions of ion exchange functional groups on both the surface hydrophobicity (Figure 19) [104].…”

Characterization of Ferrofluid-Based Stimuli-Responsive Elastomers

“…Fillers, mostly in the form of powders with submicrometer or nanometer particle sizes can provide the required properties to the SRM, including magnetic (Filipcsei et al, 2007), electric (Roy et al, 2010;Taleb et al, 2014), mechanical (Sagara and Kato, 2009;Shanmuganathan et al, 2010), or optic (Giammanco et al, 2015;Seo et al, 2015) properties. With regards to the matrix itself, organic and inorganic materials have already been used (Roy et al, 2010).…”