基于聚β-环糊精模板效应的可拉伸功能性超分子水凝胶

Stretchable and Functional Supramolecular Hydrogels Based on the Template Effect of Poly(β-cyclodextrin)

以β-环糊精与环氧氯丙烷的线形共聚物为大分子主体,以亲水性短链修饰的含可聚合双键的二茂铁单体为客体分子,利用二者间的主-客体包结络合作用,制备了一种新型的"大分子超分子交联剂".进而借助聚β-环糊精的大分子超分子模版效应,通过简单自由基共聚合反应,实现了基于β-环糊精与二茂铁客体分子间包结络合作用的可超长拉伸、抗刺、黏附性超分子水凝胶的制备.

β-cyclodextrin-ferrocene host-guest inclusion complex has been widely used to construct various functional functional supramolecular hydrogels, but all these reported hydrogels are often very weak and/or brittle. In this work, β-cyclodextrin （β-CD） based linear copolymer （polyβ-CD） was synthesized and used as the macromolecular host, hydrophilic and βexible spacer modified ferrocene （Fc） monomer acted as the guest. The polymerizable Fc monomer was preloaded on polyβ-CD to form a novel type of ＇macromolecular supramolecular cross-linker＇ （MSCL） owing to the inclusion complexation between β-CD and Fc. For the first time, stretchable, stab-resistant and adhesive supramolecular hydrogels were prepared via simple free-radical copolymerization of MSCL and acrylamide. Tensile-testing results showed that the obtained supramolecular hydrogel can be stretched up to more than 30 times of its original length without breaking. The gel can also be stabbed by sharp tips of scissors or pencil without fracture, indicating excellent stab resistance property. At the same time, the hydrogel also exhibited strong adhesion to the surfaces of human hand, hydrophilic glass or hydrophobic porcine skin. We attribute these distinguished behaviors to the successful use of polyβ-CD and the introduction of βexible hydrophilic spacer to the Fc monomer. Firstly, polyβ-CD acted as a macromolecular supramolecular imprint to form pre-organized Fc- polyβ-CD complexes, and thus resulted in relatively local high density of pendent Fc groups in the polymeric network. This is different from most of the reported host-guest interaction based supramolecular hydrogels, where the host and guest groups are randomly attached in the polymeric network. Secondly, after copolymerization, polyβ-CD was homogeneously immersed in the network by noncovalent interaction but not covalently conjugated in the network, which would greatly limit its mobility. Finally, the introduction of hydrophilic spacer on Fc not only can yield water soluble Fc-polyβ-CD macromolecular supramolecular complex, but also provide the released free Fc groups with more βexibility. Altogether, the local high density of both the guest and host groups in the network combined with their relatively high βexibility provided the present supramolecular hydrogels with excellent mechanical properties.