Hydrogels assembled by inclusion complexation of poly(ethylene glycol) with alpha‐cyclodextrin

Polymeric hydrogels were prepared based on the inclusive complexation between α‐cyclodextrin (α‐CD) and poly(ethylene glycol) (PEG). Because the rheological property of a thermodynamic stable hydrogel should be gap‐independent, it is found in this work that the uniformed hydrogel can be distinguished from gel‐like aggregation by changing the plate gap during the rheological measurement. By this rheological method it is determined that suitable storage duration is necessary for the preparation of uniform hydrogels. However, the sonication technique after mixing CD and PEG solutions or increasing PEG concentration can shorten the time to form stable hydrogels. Moreover, the molecular weight of PEG should be high enough (≥8000 g/mol) for sol‐gel transition. The higher the molecular weight of PEG is, the longer storage time is needed to obtain a uniform hydrogel. From the observation by differential scanning calorimetry (DSC) and X‐ray diffraction (XRD) of prepared hydrogels, we concluded that the driving force of networks should be attributed to the crystallization of complexed α‐CDs in the α‐CD/PEG pseudo‐polyrotaxanes.