Study Of Cyclodextrin Host-Guest Interaction By Spectroscopic Methods

In recent years, cyclodextrins (CDs) and their derivatives are widely used in the fields of food, drugs, environment protection and so on because of the excellent property of inclusion.In this thesis,β-CD and dansyl group substituted poly(acrylic acid) (PAAβ-CDen and PAADSen) were synthesized. The association constants between a variety of CDs and dansyl amide(DNSA) or PAADSen were determined by steady-state fluorescence spectroscopy. Polymer netwotks based on self-assembly of PAAβ-CDen and PAADSen were bulit and characterized by rheological and UV-Vis methods.(1)The synthesis of PAAβ-CDen can be divided into three steps. Firstly, monosulfonatedβ-cyclodextrin (β-CD-6-OTs) was obtained from the reaction bwtweenβ-CD and p-toluenesulfonyl chloride. Secondly, monoaminoβ-CD (β-CD-6-EDA) was obtained from the reaction betweenβ-CD-6-OTs and ethylenediamine. At last,β-CD-6-EDA was grafted onto PAA to get PAAβ-CDen. As for PAADSen, similar procedure was followed:firstly monoamino product of dansyl chloride was synthesiszed with dansyl chloride and ethylenediamine and then the monoamino product was grafted onto PAA to get PAADSen.(2) By steady-state fluorescence spectroscopy, the association constants betweenα-,β-, y-CD and DNSA or PAADSen were determined separately and the effects of ionic strength and polarity of solvent on association constant were studied separately. The results indicate that,α-CD can't bind DNSA and PAADSen into its cavity,β-CD's capacity of binding DNSA or PAADSen is stronger thanγ-CD's; the introduction of PAA chain can reduce the binding capacity of cyclodextrins to dansyl groups grafted in PAA, this phenomenon is more obvious forβ-CD/PAADSen inclusion thanγ-CD/PAADSen inclusion; the association constant increase with the ionic strength increasing; the association constant decrease with decreasing polarity of solvent.(3) Rheological method was used to confirm the structure of networks formed by PAAp-CDen and PAADSen. The association constant between dansyl group andβ-CD group was determined by UV-Vis spectrometry method. The results show that, the viscosity of PAAP-CDen/PAADSen mixture is bigger than the single polymer. which accounts for the formation of polymer networks; the stoichiometric ratio ofβ-CDen and DSen is 1:1 because the maximum mixture viscosity occurs at this ratio; the association constant ofβ-CDen/DSen (K=27.5±3dm3·mol-1) is much smaller than that ofβ-CD/DNSA (K=103±5dm3·mol-1).