| Positron annihilation technique(PAT) is a unique sensible method to probe defects or free volume properties in materials based on time and momentum information of photons produced by positron-electron annihilation. It is of great significance to explore application of PAT in functional polymeric system. The study of positron annihilation mechanism is necessary due to the complicated process of positronium formation and annihilation in polymers.In this thesis,we investigate the structure and water sorption capability of chitosan metal complexes with different metal contents,different metal species and salt by FTIR,XRD,UV-vis and PAT. In addition,we have emphasized to study formation and annihilation of positronium in polymeric system with.The main contents as follows:1. Chitosan-Pd2+complexes with various Pd2+concentrations were prepared through the sol-gel method.The change of positronium annihilation lifetime and intensity with metal contents increasing has been discussed in comparison with that of power samples.Finally,the conclusion is obtained that Cl-in complexes is a main inhibitor for positronium formation.2. Metal interaction with chitosan was studied by FTIR and UV-vis in chitosanNi complexes with various metal ions contents.Crystallinity of complexes has intimate connection with metal contents explored by XRD.Furthermore, formation of positronium is inhibited by the existence of NO-3/Cl-/Ac-in the polymeric system. Meanwhile, positronium lifetime is invalid to estimate free volume size in materials based on semiempirical equation. In addition,CDB is fully sensitive to chemical composition in the complexes.3. Chemical environment in positron annihilation sites of Co2+,Ni2+,Cu2+and Zn2+supported chitosan complexes was investigated by coincident Doppler broadening spectroscopy. |
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