Self-healing Alginate Hydrogels Based On Supramolecular Interaction

Alginate, which is extracted primarily from brown algae, is a kind of natural polymers. Due to its biocompatibility, bioadhesiveness and biodegradability, alginate can be investigated and used for many biomedical applications such as drug delivery and tissue engineering. However, research on self-healing alginate hydrogels is little. Alginate hydrogels with self-healing ability can be more helpful when used for drug delivery and other applications. Nowadays, researchers tend to use the intrinsic features of the molecular structure to obtain the self-healing performance, which is the self-heal based on supramolecular interaction. In this thesis, two kinds of supramolecular interactions—hydrogen bond and host-guest interaction — will be brought to the sodium alginate system, and self-healing sodium alginate hydrogels will be prepared. The main research and results are summarized as follows:(1) We prepared poly(acryloyl 6-aminocaproic acid)(PA6ACA) hydrogels with different crosslinker content. The influence of crosslinker content on the mechanical and self-healing performance were tested and analyzed. The tensile strength and Yong’s modulus increased with the increasing of the crosslinker content, while the breaking elongation and the self-healing ratio decreased. We analyzed the results with two factors, one was the hydrogen bond strength between the healing interfaces, the other was the bulk strength of the hydrogel. Then, the optimal formulations were selected and brought to the sodium alginate hydrogels. The PA6ACA/SA Semi-IPN hydrogels with perfect self-healing performance were prepared successfully. Also, crosslinker and SA content influenced the mechanical and self-healing performance. We tested the hydrogels and analyzed the results.(2) The PA6 ACA chains were covalently grafted to the sodium alginate chain, then the SAg-PA6 ACA hydrogels with good self-healing performance were prepared successfully. We discussed the influence of crosslinking density on the self-healing performance. The experiment data manifested that crosslinking density had great impact on the self-healing performance. With the crosslinking density increasing, self-healing performance became bad. We also compared the mechanical and self-healing performance of the two kinds of hydrogels— SAg-PA6 ACA hydrogel and PA6ACA/SA Semi-IPN hydrogel, and analyzed the influence of different network structures on the performance, which were grafting network and Semi-IPN network, respectively.(3) β-Cyclodextrin(β-CD) were grafted on the oxidezed sodium alginate(OSA) chain, and the adamantyl acrylamide(Ad-AAm) were copolymerized with acrylamide, then, the OSA-g-β-CD/ PAM-Ad hydrogel based on host-guest interaction were prepared. We tested the viscoelasticity, mechanical property and self-healing performance of the hydrogel. Rheologic characterization manifested that, there were 3D network structure in the OSA-g-β-CD/ PAMAd hydrogel. So, host-guest interaction exists between β-Cyclodextrin group and adamantine group. The complex became the crosslinking points of the system and made the system soft solid. Tensile experiments showed that the hydrogel had good self-healing performance. The self-healing ratio was 72%. Competitive experiment demonstrated that the self-healing behavior resulted from the host-guest interaction between the healing interfaces.