Dependence of Slippery and Elastic Properties of Thin Polymer Films on the Grafted Flexible Sidechain Amount

In modern life, people face a wide number of sticky problemswhenadhesion is highly undesirable: water and dirt stick to clothes, usefulmaterials stick to the walls of their containers and cannot be fullyused, water sticking and freezing on airplane wings affects handlingand can be dangerous, biological liquids can stick and form clotsinside medical devices threatening patients' lives, etc. Slipperyliquid-infused porous surfaces (SLIPSs) with pressure stable omniphobicitycould help to solve these issues. Lubricant depletion from poroussurface and subsequent degradation of omniphobic properties is themajor problem for SLIPS. It could be resolved by attaching flexible,liquid-like sidechains to the polymer matrix. Understanding the relationshipbetween the structure of such polymer films and wetting effects istherefore of great importance. The present work is devoted to thestudy of droplet pinning on crosslinked polydimethylsiloxane (PDMS)polymer films with varied amounts of attached flexible PDMS sidechainsand clarification of the relationship between slippery and viscoelasticproperties of the films. An one-stage approach to the synthesis ofsuch slippery coatings on smooth and porous substrates in eco-friendlypressurized CO2 solutions is proposed. Pinning force andYoung's modulus (E) of the films on siliconsubstrates with variation of the grafted sidechains amount (x) are measured. The non-monotonic dependence of the pinningforce on the amount of sidechains is obtained: the pinning force decreasesat small x values (region I) and starts to increaseat higher x (region II). The effects of the graftedsidechains amount, as well as matrix softening, are discussed foreach case. It is demonstrated that the proposed method of film synthesisallows one to obtain thin, uniform coatings on fabrics without gluingthe fibers. Such coatings with an optimal amount of PDMS sidechainsdemonstrate decreased sliding angles for droplets of water and aqueousalcohol solutions, as compared to PDMS coatings without grafted sidechains.The proposed technique may be of interest for deposition of coatingson porous surfaces having a complex morphology, such as textiles,aerogels, porous electrodes, etc.

Automated summary

In modern life, people encounter various problems caused by adhesion, such as clothes getting dirty, useful materials sticking to containers, and water freezing on airplane wings. Slippery liquid-infused porous surfaces (SLIPSs) could potentially solve these issues. This study focuses on the relationship between the structure of polymer films and wetting effects, aiming to understand and improve the properties of SLIPS. The researchers proposed a new method to synthesize slippery coatings on smooth and porous substrates using eco-friendly CO2 solutions, and demonstrated the effectiveness of this technique on various surfaces.