A tough self-assembled natural oligomer hydrogel based on nano-size vesicle cohesion
Shellac is an ancient oligomer and had been widely used in many fields in the past. Recently, we found that these low-molecular weight, biodegradable and amphiphilic biomacromolecules could aggregate to fabricate multi-scale materials. In this study, gluconic acid lactone (GDL) was employed as a H+ donor, and mixed with shellac-COONa to prepare a shellac hydrogel. It was found that in the beginning of gelation, as the hydrolysis of GDL proceeded, the amphiphilic molecules shellac-COONa changed to shellac-COOH and assembled into the nano-size vesicles. Furthermore, these vesicles constructed by shellac-COOH, similar to asymmetric gemini surfactants, could aggregate together to fabricate the network of the shellac hydrogel by the hydrophobic association between two sets of short hydrophobic chains from two adjacent vesicles. The shellac hydrogel has excellent mechanical properties and nice degradation behavior, and the compressive fracture stress, strain and compress modulus could be 7.6 MPa, 43.7%, 61 MPa, which means it can be used as a new kind of soft material, such as high mechanical performance bio-based foams.