Agarose Facilitating Functional Hydrogels

Agarose is polysaccharide that is extracted from seaweed and has amply been applied, e.g., in biological characterizations. It forms hydrogels by physical crosslinks, showing thermoreversible sol-gel transitions, wherein nanoscopic bundles of semiflexible fibrils are formed in the gel state in comparison to polymer coils in the sol state. In hydrogels it allows strain stiffening (1). Here we show that agarose facilitates new hydrogelation functionalizations. We combine agarose physical gel networks with poly(N-isopropylacrylamide), PNIPAm, chemical gel networks. PNIPAm classically shows Lower Critical Solution Temperature (LCST) thermoresponsive behavior. Upon removing the agarose network, emptied channels remain facilitating rapid water flow (2). Such channelled PNIPAm gels are transparent at room temperature, but show intense white colour upon heating. Chemically modified agarose can also be used as a chemical macro-crosslinker therein to allow even promoted whiteness upon heating (3). Similarly, upon removing the agarose network to allow channeled PNIPAm hydrogels allows rapidly thermally switchable underwater adhesion taken that PNIPAm has been functionalized with catechol (4). Finally, thermally trainable mechanical and volumetric properties are shown using networks consisting of PNIPAm and agarose or acrylated agarose (5). The approaches suggest that agarose is a versatile polysaccharide to functionalize composite hydrogels, relevant in foreseen applications.<br/><br/>1. L. Martikainen, K. Bertula, M. Turunen, O. Ikkala, Macromolecules, 53, 9983, 2020<br/>2. A. Eklund, H. Zhang, H. Zeng, A. Priimagi, O. Ikkala, Adv. Funct. Mater., 30, 2000754, 2020.<br/>3. A. Eklund, S. Hu, Y. Fang, H. Savolainen, H. Zeng, A. Priimagi, O. Ikkala, H. Zhang, submitted, 2023.<br/>4. A. Eklund, O. Ikkala, H. Zhang, Adv. Funct. Mater., 2214091, 2023<br/>5. S. Hu , Y. Fang , C. Liang, M. Turunen, O. Ikkala, H. Zhang, Nat. Commun., 14, 3717, 2023