Abstract
Biopolymer materials have been considered a “green” alternative to petroleum-based polymeric materials. Biopolymers cannot completely replace synthetic polymers, but their application should be extended as much as possible, exploiting the benefits of their low toxicity and biodegradability. This contribution describes a novel strategy for the synthesis of super-macroporous 2-hydroxyethylcellulose (HEC) cryogels. The method involves cryogenic treatment of an aqueous solution of HEC and citric acid (CA), freeze drying, and thermally induced crosslinking of HEC macrochains by CA in a solid state. The effect of reaction temperature (70–180 °C) and CA concentration (5–20 mass % to HEC) on the reaction efficacy and physico-mechanical properties of materials was investigated. Highly elastic cryogels were fabricated, with crosslinking carried out at ≥100 °C. The storage modulus of the newly obtained HEC cryogels was ca. 20 times higher than the modulus of pure HEC cryogels prepared by photochemical crosslinking. HEC cryogels possess an open porous structure, as confirmed by scanning electron microscopy (SEM), and uptake a relatively large amount of water. The swelling degree varied between 17 and 40, depending on the experimental conditions. The degradability of HEC cryogels was demonstrated by acid hydrolysis experiments.
Highlights
Natural polymers, referred to as biopolymers, have attracted considerable attention in the last decade as a “green” alternative to petroleum-based polymeric materials [1]
33..DDiissccuussssiioonn We introduced a novel strategy for fabricating green super-macroporous cryogel materials based on the chemical crosslinking of HEC with citric acid (CA) in a solid state
Super-macroporous degradable cryogels were synthesized by a novel strategy involving thermally induced crosslinking of HEC with CA in a solid state
Summary
Referred to as biopolymers, have attracted considerable attention in the last decade as a “green” alternative to petroleum-based polymeric materials [1]. Cryogels are super-macroporous hydrogels synthesized by applying cryogenic treatment of gel-forming systems [9] This system could be an aqueous solution of monomer or polymeric precursor and an initiator. Cryogels of cellulose derivatives were prepared by UV-induced crosslinking or reactions with chemical reagents. The interconnected macroporous structures of the cellulose-based cryogels were strongly influenced by the amount of crosslinker and extra water added in the process of cryopolymerization. The crosslinking of cellulose derivatives via UV irradiation of the frozen aqueous solutions of the polymers has been considered a convenient method for fabricating biodegradable cryogels [11]. To improve the safety of both the final product and the manufacturing process, nontoxic, water-soluble citric acid (CA) was used to crosslink cellulose derivatives in aqueous media [15].
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