Posted by The cross-linking point of a conventional chemical cross-linking agent is fixed. Therefore, gels that are prepared with a conventional cross-linking agent have poor deformability, strength, shear resistance, and further properties. Some researchers have prepared a new cross-linking agent using cyclodextrin (CD). In a polyrotaxane cross-linking agent, the cross-linking points can slide freely along the molecule chain. The special “slide ring” structure can provide better elongation, strength, and other properties to gels, which can effectively expand the application of the gel’s materials. This paper summarizes the preparation methods and applications from different types of CD and compares the improvements of properties (swelling, viscoelastic properties, etc.).
At present, the preparation methods of polyrotaxane cross-linking agents based on α-CD are more mature than β-CD and γ-CD. However, some factors also limit the use of the cross-linking agent. On the one hand, the expensive price of α-CD limits its application, so the cheaper β-CD has become a potential material for development. On the other hand, it is necessary to find a convenient and simple method to prepare polyrotaxane cross-linking agent to avoid the cumbersome preparation process. Furthermore, some CD may fall out from the long-chain molecule during the preparation process, which may affect the properties of the hydrogel.
The single chain of the guest molecule passes through the cavity of α-CD or β-CD, whereas the situation that two chains pass through the cavity may occur in γ-CD. The difference makes γ-CD polyrotaxane cross-linking agents have some special preparation methods and properties.
Liu, S.; Zheng, J.; Wang, J.; Liu, S.; Zhang, X.; Bao, D.; Zhang, P. Preparation and Application of Polyrotaxane Cross-Linking Agent Based on Cyclodextrin in Gel Materials Field. Gels 2023, 9, 854. https://doi.org/10.3390/gels9110854