Studies On Chemical Modification And Properties Of Poly(ε-caprolactone)

Poly(ε-caprolactone)(PCL), a biodegradable and biocompatible polymer, has found applications in drug delivery device, medical apparatus and other environmentally friendly materials. However, because of its slow degradation, poor water-solubility and the lack of functional groups along the polyester backbone, their biomedical applications are limited. So it is necessary to study on chemical modification and properties of PCL. In this Ph.D. thesis, we have successfully synthesized the copolymers of ε-caprolactone(CL) and1,3-dioxolan-2-one(DOO)(or N,N-dimethylaminoethyl methacrylate(DEM)) with the catalyst of metal-free phosphazene base (t-BUP4). Meantime we initiated ring-opening polymerization of e-caprolactone on SiO2nanosphere surface with the catalyst (t-BuP4). We have investigated chemical modification and properties of PCL. More specifically, we have1. synthesized the poly(CL-co-EC-co-EO) copolymer via ring-opening copolymerization of CL and DOO with the initiator. The copolymers have been characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC), polarizing optical micrograph (POM), differential scanning calorimeter (DSC) and wide-angle X-ray diffraction (WAXD). Such poly(CL-co-EC-co-EO) copolymer is random. The effects of the monomer feed ratio, temperature and catalyst content on the polymerization have been examined. Moreover the enzymatic degradation of the copolymer with high CL content has been investigated by use of quartz crystal microbalance with dissipation (QCM-D). Our studies demonstrate that as the CL content decreases, the crystallinity and crystal size decrease, and the enzymatic degradation rate increases. The copolymer exhibits uniform degradation.2. successfully prepared the poly(CL-co-DEM) copolymers by hybrid copolymerization of CL and DEM, and obtained the polyampholyte by betainization of poly(CL-co-DEM) copolymer with1,3-propane sultone. The results of FTIR, NMR and GPC measurements indicate that the poly(CL-co-DEM) copolymer is random and amphiphilic. DSC and TGA results demonstrate that the copolymers have poor crystallinity, indicating that introducing of DEM disorganized CL segments. Meanwhile by dynamic laser light scattering (DLS) and QCM-D we study on the self-assembly behavior and protein adsorption of the copolymer and polyampholyte in phosphate buffered solution. The results show the polyampholyte has good protein resistance.3. initiated ring-opening polymerization of CL on well-defined SiO2nanosphere surface with the catalyst (t-BuP4). The surface molecular structure of the SiO2-g-PCL nanospheres was characterized by FTIR, NMR, XPS and TGA measurements. Crystallization behavior of PCL/SiO2nanocomposites was investigated by POM, DSC and WAXD measurements. The presence of SiO2affects the crystalline temperature (Tc), melting temperature (Tm) and the glass transition temperature (Tg) of PCL. Moreover the enzymatic degradation has been investigated by QCM-D and Our studies demonstrate that as the SiO2content increases, the enzymatic degradation is uneven with high rate.4. directly prepared Polyamide1010(PA1010) by in-situ melt poly condensation in the presence of-NH2nanospheres. The results of FTIR, NMR, XPS and TGA measurements demonstrate that the SiO2nanosphere is encapsulated by PA1010chains. WAXD and DSC measurements show that the PA1010/SiO2-NH2nanocomposites have a lower crystallinity (χc) in comparison to PA1010. In comparison to pure PA1010, the nanocomposites show higher Tc and Tg, and tensile strength and storage modulus also were improved.