Molecular Understanding and Design of Porous Polyurethane Hydrogels with Ultralow-Oil-Adhesion for Oil–Water Separation

Materials with opposite affinities toward oil and water have been extensively used to coat porous substrates for oil-water separation, but the applications of these materials have been limited by the need for complex coating processes as well as the short-term adherence of these materials onto different substrates under extreme conditions. As reported herein, the robust porous polyurethane hydrogel has been theoretically and structurally designed with ultralow-oil-adhesion properties which is free stand without depending on additional substrates. The combination of superhydrophilic properties along with the underwater superoleophobic behavior of this porous hydrogel allows gravity driven separations of oil-water mixtures, and its antiadhesion performance toward oil prevents undesirable oily fouling. The underwater superoleophobic properties were also illustrated by molecular dynamics simulation to understand the resisting effect of hydrated layers. The as-prepared porous hydrogel shows ultrahigh oil-water separation efficiencies of 99.9% for various oil-water mixtures, ranging from those containing viscous oils (pump oil and peanut oil) to organic solvents (n-hexane, n-hexadecane, and toluene). In addition, this hydrogel is durable even with exposure to various harsh conditions including acidic and basic media (pH 0-14) as well as exposure to mechanical abrasion. We believe that the combination of facile preparation, substrate independence, gravity driven separation, antifouling properties, high durability, as well as the outstanding separation flux and efficiency of this robust porous hydrogel will help to advance the design and application of materials in oil-water separation fields.