Supramolecular Modification Of Poly(p-dioxanone)

Poly(p-dioxanone)(PPDO),an important biodegradable aliphatic poly(ether-ester),has attracted considerable attention in recent years because of its excellent biocompatibility,biodegradability and flexibility.Due to the intrinsic hydrophobicity along with its lack of specific biological properties,the high crystallinity and discontinuous degradation rate of PPDO limit the widely application of PPDO.In this thesis,PPDO is modified by cycldextins(CD)using the method of supramolecular chemistry at the molecular.The optimum reaction conditions is explored by changing the reaction solvent,reaction temperature,reaction time,mass ratio,and the precipitation reagent.Three kinds of novel pseudo-polyrotaxanes(PPRs)consisting of PPDO and ?-CD,?-CD,?-CD(with different ratio)were successful obtained via heat-cool(H-C)cycles.The self-assembly material has been characterized by Fourier transform infrared spectroscopy,polarimeter,wide-angle X-ray powder diffraction,NMR and AFM,and the thermodynamic properties,hydrophilic,the crystallization and hydrolytic degradation were studyed,the following innovative achievements and progresses were exhibited.(1)The optimum conditions for preparing PPRs to achieve the highest yield of 87.5%were as follows:PPDO dissolved in N,N-dimethylformamide(DMF)at 60?,reaction time 72 h(3 times H-C cycles)and ether as the precipitant.(2)The PPRs were further investigated by FT-IR,wide-angle X-ray diffraction,two-dimensional nuclear magnetic resonance and thermogravimetric analysis.All the studies supported the formation of proposed PPRs.When CD/PPDO feeding ratio is 3:1,the assembly effect is good,and the highest yield was achieved.(3)The thermal stability experiment indicated that the thermal stability of PPDO in PPRs was significantly improved compared with free PPDO by the cyclodextrins.Static water contact angle tests demonstrated that the hydrophilicity of PPDO had significantly enhanced by the cyclodextrins.(4)The polarizing microscope observations was used to survey the crystal morphology,and those tests told us that small amount of cyclodextrins will not affect the crystallization of polymer materials performance,but crystal morphology will be irregular crystal instead of large spherulite with the increase of content of cyclodextrins.(5)Hydrolytic degradation experiments showed that the PPRs had different degradation behaviors compared to the pure PPDO,and the degradation rate can depend on the amount or the type of cyclodextrin.