The Preparation Of Cyclodextrin/biodegradable Inclusion Complexs And Their Application As The Nucleating Agents For Crystallization

Cyclodextrins are able to include various guests inside their cavities due to their hydrophilic outers and hydrophobic cavitives. It found that cyclodextrin can form inclusion complexes not only with organic molecules, inorganicions as well as small biomolecules but also polymers with long molecular chain. The inclusion complexes are widely used in structure control of materials, tissue engineering and so on. Cyclodextrin/biodegradable polymer inclusion complexes have also been drawn much attention. Further more, the inclusion complex can improve the crystalline properties of polymer as a new green nucleation agent.In this thesis, the inclusion complexes between cyclodextrin and poly(lactic acid)(PLA), cycodextrin and poly(3-hydroxybutyrate-co-4-hydroxybutyrate)[P(3HB-co-4HB)] were prepared, respectively. The nucleation efficiency of inclusion complexes was also studied. The main work and innovations of this work are as follows:(1) The inclusion complex between PLA and cyclodextrin (PLA-IC) was prepared by drop wise method. The mixed solution of host and guest was stirred, followed by filtration, washing, and dry, the white solid complex can be obtained at last. The characteristic diffraction peak of cyclodextrin inclusion complex located at20°was observed at the wide-angle X-ray diffraction (WAXD) spectrogram of PLA-IC, which is corresponding to channel structure based cyclodextrin inclusion complex. It is suggested that the PLA chain was included in the cavities of cyclodextrin. PLA-IC was also characterized by the measurements of differential scanning caborimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). Moreover, the influence of steric configuration and molecular weight of PLA on the inclusion complex formation was analyzed in the thesis.The effect of PLA-IC as a nucleation agent on the PLA crystallization behavior was studied firstly in this thesis. The crystallization behaviors and spherulite morphologies of PLA were studied by DSC and polarized optical microscopy (POM). The results show that compared to cyclodextrin, PLA-IC can accelerate the crystallization rate of PLA. The reason may be attributed to the partially crystallization of the uncovered segment of PLA by cyclodextrin cavities, which can induce the bulk crystallization of PLA.(2) The preparation of inclusion between cyclodextrin and P(3HB-co-4HB) was reported firstly in this thesis. The inclusion complex between cyclodextrin and P(3HB-co-4HB) was successfully formed by co-solution method and the process is similar to that of PLA-IC. The inclusion complex was then characterized by WAXD, DSC and FTIR. Moreover, the effect of molecular weight and space structure of P(3HB-co-4HB) on the formation of inclusion complex was also discussed in this thesis.The effect of inclusion complex on the crystallization behavior of P(3HB-co-4HB) was studied by DSC and POM. Different from that of PLA-IC, the results show that the nucleation efficiency of inclusion complex is more or less than that of cyclodextrin. The reason may be that the P(3HB-co-4HB) loses its nucleation ability above melt temperature, which is much higher than its melt temperatute.