A simple preparation method of rotaxane cross-linker based on γ-cyclodextrin and its application in hydrogel materials

Currently, preparation of rotaxane cross-linker (RC) requires at least two-step or more complex chemical reactions. Therefore, a simple and efficient method is proposed to prepare RC based on γ-Cyclodextrin (γ-CD), which requires only one-step chemical reaction. This means that it is more convenient to apply RC to prepare hydrogels with pulley effect. The structures of RC are characterized by 1H NMR, 2D NOESY NMR, DOSY NMR, XRD and thermal gravimetric analysis. And the effects of reaction conditions on the yield of RC are studied. RC and traditional cross-linker (N, N′-Methylenebis(acrylamide), MBA) are, respectively, can be copolymerized with acrylamide (AM) to prepare hydrogels to compare the swelling ratios and deformation properties of hydrogels. Furthermore, the effect of mineralization degrees on the swelling ratios of hydrogels and the effect of hydrogels prepared with different content of cross-linker on deformation properties are explored. After absorbing water for 200 h, the swelling ratio of slip-ring hydrogel0.5 % (% is the weight percentage of cross-linker to AM) is 79.05, while that of traditional hydrogel0.5 % is 8.8. The elongation at break of traditional hydrogel0.6 % (211 %) is much smaller than that of slip-ring hydrogel0.6 % (6467 %) and the compression modulus of traditional hydrogel0.6 % (0.20 MPa) are greater than that of slip-ring hydrogel0.6 % (0.11 MPa). Thus, the swelling ratios and deformation properties of hydrogel prepared by RC are better than that of hydrogel prepared by traditional cross-linker. Lastly, the seepage properties of hydrogel dispersions in porous media are also investigated. The hydrogel dispersion prepared by RC has lower injection pressure and higher residual resistance coefficient than that of traditional cross-linker.