Study On Supramolecular Assembling Based On Cyclodextrin And Long-chain Aliphatic Diacids

In supramolecular chemistry, it is important to study the self-assemblingbehaviors through molecular-recognition with cyclodextrins as the host molecules.In this paper, based on the preparation of inclusion complexes (ICs) betweenβ-cyclodextrin(β-CD) and a series of long-chain aliphatic diacids(DAn,n varing from11 to 15), the supramolecular assembling behaviors of the above systems werestudied and the corresponding ICs were characterized to determine theirpseudorotaxane structures. The ICs ofβ-CD and a,?-alkanedicarboxylate anions(DAn^2-) were acquired and the structure together with the conformation in aqueoussolution was characterized and proved to be also a pseudorotaxane structure. A seriesof amphiphilic condensation polymers(polyesters) were synthesized utilizing thephobic chains of DAn by condensation polymerization with PEG andmono-hydoxyl-PEG, then the inclusion behaviors between these polymers andβ-CDwere studied and the process,the michanism of ICs-forming systems wereinvestigated. All the details are as follows:1.The inclusion complexes ofβ-CD and DAn were prepared by co-precipitationand co-grinding via supramolecular assembling and the formation of ICs wereconfirmed by means of FTIR,DTA,elementary analysis and XRD analysis; thestoichiometry ofβ-CD to DAn was 2:1 and theβ-CD molecules were accomodatedon the aliphatic chain of DAn to form a columar [3]pseudorotaxane structure.2. On the basis of the ICs ofβ-CD and DAn,β-CD and a,?-alkanedicarboxylateanions (DAn^2-) were acquired by neutrilization with base and the [3]pseudorotaxanestructure was maintained by FFIR and H-NMR analysis.3. By comparing the H-NMR spectra of the IC ofβ-CD and a,?-alkanedi-carboxylate anions with 1:1 molar ratio with that of 2:1, it is reached that in the 1:1IC, the methylene chain of DAn^2- adopts a gauche kink conformation and themaximum number of carbon atoms in the aliphatic hydrocarbon chain is 8. Otherwise,the methylene chain of DAn^2- in 2:1 IC adopts a trans-conformation to make 4 carbonatoms in the aliphatic hydrocarbon chain resided in oneβ-CD molecules. 2D-NOSEY spectrum ulteriorly confirmed that the including mode was a [3]pseudorotaxanestructure.4.A series of amphiphilic condensation polymers(polyesters) were synthesizedutilizing the phobic chains of DAn by condensation polymerization with PEG andmono-hydoxyl-PEG. The inclusion behaviors between these polymers andβ-CD werestudied and ICs of CP613,CP1113,CP2013 were acquired by co-precipitation fromβ-CD saturated aqueous solution and seperated by centrifugation.5.The formation of ICs above was confirmed by FTIR,XRD and H-NMRspectra and the accomodating situations were determined by the shape of NMRresonance peaks and the stoichiometry of the complexes is ofβ-CD to DAn wasachieved by calculation of area integral.6.Especially for CP1113 synthsized by DA13 condensating withmono-hydroxyl-PEG, which has a specific tri-block structure, the process of theIC-forming was studied by UV-vis spectrum,DSC,TG and H-NMR analysis and thethe stoichiometry ofβ-CD to PEO segments was 7.5:1, so part ofβ-CD moleculeswere accomodated on the hydrofobic methylene chain and most ofβ-CD moleculeswrapped on PEO segments of CP1113.7. No inclusion complex of CP1102 was formed possibly due to the shorterhydrofobic hydrocarbon chain and the weaker interactions withβ-CD led to thedifficulty for supramolecular assembling. For CP5013, which was synthesized byDA13 and PEGS000, no inclusion complex was observed beacause the longer PEOchain and the higher energy level blocked theβ-CD molecules to thread. A inclusioncomplex-forming model was put forward according to the above experimental resultsand the model could explain the forming mechanism of all these ICs formed bycondensation polymers withβ-CD supposing the model was appropriately adjusted.