Study And Application Of Lower Critical Solution Temperature(LCST) Phenomenon Of Cyclodextrin In DMF Solution

Cyclodextrins?CDs?have been widely used to constructing various well-defined microstructures,such as core-shell micelles,vesicles,and polyrotaxanes,simply via the self-assembly of CDs with guest molecules.However,the native CDs are highly crystalized with a cage-type structures that the CD molecules are randomly assembled so the holes of CDs are blocked by neighboring CDs.Arranging pure CDs in an order way to expose their holes remains a great challenge.In this work,two novel crystal structures of?-CD and?-CD are created simply by heating up their DMF solution to 70?.The crystal space group of?-CD changes from monoclinic to tetragonal and shows ideal cubic shape,whereas the?-CD forms a hexagonal column morphology,as revealed in SEM.The XRD results indicate that both the?-CD and?-CD changes from cage-type into hole-opened type crystal structures since the head-head and tail-tail arrangement,which endows a simple method to orderly assembling CD molecules and thus opening their pores.Besides,the thermal stability and chemical structures are not influenced as demonstrated by TGA,solid state ¹³C NMR and FTIR.Furthermore,this novel nanotube crystal structure was used in cloud point separation in waste water or the adsorption of molecules.Besides,the novel crystal was modified to load metal ion and cross-linked to realize versatile application.In summary,DMF is found as an inducer to shape the self-assembling of CDs and give birth to new crystal structures.The molecular scale ordering assembly of CDs with open holes may give a new point of view in many fields.