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We present mechanically strong macroporous, squeezable dextran cryogels as a column filling material for the removal and separation of binary organic dye and pesticide mixtures from aquatic medium. Dextran cryogels were prepared from aqueous solutions of dextran of various molecular weights (MWs) in the presence of 20 to 50 mol% divinyl sulfone (DVS) as a cross‐linker at −18°C. The cryogels have interconnected irregular pores of 100 μm in sizes, and exhibit 69‐84% reversible squeezability without damaging the 3D dextran network. Their total open pore volumes (6.3‐10 mL g−1), weight swelling ratios in water (1380%‐2200%), and mechanical parameters could easily be adjusted by both DVS mol% and MW of dextran. Dextran cryogel with the highest modulus (3.8 ± 0.5 MPa), compressive stress (8 ± 2 MPa) and plateau stress (0.46 ± 0.04 MPa) was obtained at 50 mol% DVS using dextran with a MW of 15 to 25 kg·mol−1. Dextran cryogels are hydrolysable at pH = 1 and 9 but stable at 7.4 independent on both the degree of cross‐linking and MW of dextran. At below 50 mol% DVS, they are blood compatible and possess slight thrombogenic effect with blood clotting index value of 98% ± 5%. They are also capable to separate binary dye and pesticide mixtures from aqueous solutions via ionic interactions.

Cryogels based on hydrophobic polymers combining good mechanical properties with fast responsivity are attractive materials for many applications, such as oil spill removal from water and passive sampler for organic pollutants. We present, here, cryogels based on butyl rubber (BR) with a high stretchability, rapid self-recoverability, and excellent reusability for organic solvents. BR cryogels were prepared at subzero temperatures in cyclohexane and benzene at various BR concentrations in the presence of sulfur monochloride (S2Cl2) as a crosslinker. Although the properties of BR cryogels are independent of the amount of the crosslinker above a critical value, the type of the solvent, the cryogelation temperature, as well as the rubber content significantly affect their properties. It was found that benzene produces larger pore volumes as compared to cyclohexane due to the phase separation of BR from benzene at low temperatures, producing additional pores. Increasing cryogelation temperature from −18 to −2 °C leads to the formation of more ordered and aligned pores in the cryogels. Increasing BR content decreases the amount of unfrozen microphase of the frozen reaction solution, leading to a decrease in the total porosity of the cryogels and the average diameter of pores. Cryogels formed at −2 °C and at 5% (w/v) BR in cyclohexane sustain up to around 1400% stretch ratios. Cryogels swollen in toluene can completely be squeezed under strain during which toluene is released from their pores, whereas addition of toluene to the squeezed cryogels leads to recovery of their original shapes.

In contrast to synthetic gels, their biological counterparts such as cells and tissues have synergistic biphasic components containing both hydrophilic and lyophilic phases, providing them some special abilities including adaptive biomechanics and freezing tolerance. Hydrogels containing both hydrophilic and lyophilic phases, referred to as organohydrogels (OHGs), are capable of mimicking the biological systems, and they might have great potential in various applications. Here, we present a facile strategy to obtain adaptive OHGs with tunable and programmable mechanics and viscoelasticity. We utilize a hydrophilic cryogel scaffold as the continuous phase of OHGs, while the pores of the scaffold act as the reaction loci for the formation of organogel microinclusions. Thus, we first prepared mechanically robust cryogels based on silk fibroin (SF) via cryogelation reactions at −18 °C. The cryogels with 94% porosity containing interconnected μm-sized pores were then immersed in an ethanolic solution of acrylic acid (AAc), n-octadecyl acrylate (C18A), N,N′-methylenebis­(acrylamide), and a free-radical initiator. Polymerization reactions conducted within the pores of the cryogels lead to mechanically strong adaptive OHGs consisting of a SF scaffold containing semi-crystalline poly­(AAc-co-C18A) organogel microinclusions. The mechanical strength of OHGs is much higher than that of their components due to the significant energy dissipation in the OHG networks. Depending on the amount of the crystallizable C18A monomer units, the melting temperature T m and the degree of crystallinity of OHGs could be varied between 49 and 54 °C and 1.3 and13%, respectively. The crystallinity created in OHGs provided them switchable mechanics and viscoelasticity in response to a temperature change between below and above T m. All OHGs exhibited shape-memory function with a shape-recovery ratio of more than 92%. The strategy developed here to obtain high-strength smart OHGs is suitable for a wide variety of combinations of hydrophilic scaffolds and organogels.