Formation mechanism of anisotropic gelatin hydrogel by self-assembly on oriented templates†

The development of structurally controlled techniques inspired by the structural formation of living systems is of great importance for the fabrication of next-generation functional soft materials using environmentally friendly processes. This study aimed to investigate the formation mechanism of anisotropic structures of the gelatin network in a hydrogel through self-assembly on oriented templates. The effects of the oriented template having a uniaxially oriented surface on the anisotropic structure of the gelatin network were influenced by the structure at different scales: molecular (the secondary structure as the microstructure on the gelatin molecule) and molecular-assembled (the morphology of the gelatin network) scales. The mechanical properties and swelling behavior of the prepared gelatin hydrogels were characterized based on the anisotropic gelatin networks. The formation of an anisotropic gelatin network by self-assembly on the oriented template was presumably achieved by a two-step process due to the following two types of structural control factors: (1) the strength of the interaction between the template and gelatin molecules, and (2) the phase separation between the gelatin and water molecules induced during the hydrogelation process. The first process involves the formation of a thin molecular layer by the interaction between the template and gelatin molecules. The second process involves phase separation between the gelatin and water molecules during the cooling process of hydrogelation. These structurally controlled techniques for the formation of polymer networks inspired by biomineralization have two application prospects, which are the construction of biological tissue-like soft materials with complex hierarchical and anisotropic network structures through self-assembly processes, and expression of biological tissue-like functions.