Hyperbranched Polyglycerols As Drug Carriers For Controlled Release And Dopant Carriers For Semiconductor Doping

Hyperbranched polyglycerols?hbPGs?are a class of globular macromolecules with a dendritic-like architecture.They exhibit some unique properties such as good synthesis controllability,abundant functionalized groups,large intramolecular cavities,low viscosity and high biocompatibility,as a result of which hbPGs as carriers may find a wide range of applications in different fields.In this dissertation,hbPGs are explored as drug carriers for controlled drug release and used as dopant carriers for semiconductor doping.hbPGs were first synthesized by ring-openning multibranching polymerization.The molecular structure and abundance of structural units?including phosphorus element abundance?were systematically characterized.The experimental results show that globular hbPGs are as large as¹0 nm in diamter with each carrying one phosphorus atom.As drug carriers,hbPGs molecules are used to carry Rhodamine B?RB?guest molecules by dissolving the hbPGs molecules in DMSO.Each hbPGs molecule carries 39 RB molecules on average.The interaction between the hbPGs and RB molecules was investigated by NMR titration and ¹H-¹H NOESY spectroscopy.The results show that the break interaction region is located at hbPGs surfaces in aqueous solution.The interaction of hbPGs and the neutral template drug 5-Fu was also investigated.It was found that 42.6%terminal T units on the hbPGs surfaces form a dense layer to blockade the encapsulation and release of guest molecules.These experiment findings have laid an important foundation for the rational design of a drug delivery system with targetability and stimuli-response properties.As dopant carriers,hbPGs molecules were grafted onto silicon surfaces via covalent bonds.Phosphorus dopants in the hbPGs monolayers were driven into silicon by rapid thermal annealing process.Secondary Ion Mass Spectroscopy?SIMS?and low temperature Hall measurements were employed to analyze the electrical activities of the phosphorus dopants.The results indicate that most of phosphorus dopants are electrically deactivated by forming C-P complex defects.To increase the ionization rate of phosphorus dopants,a pre-oxidation process?550?under O₂ambient?was developed to remove the carbon contaminants by oxydizing hbPGs into gaseous small molecules?i.e.CO,CO₂,H₂O?before the high-temperature rapid thermal annealing process was applied to drive phosphorus into silicon substrate.The experiment results show that most of carbon contaminants have been removed,as a result of which the ionization rate of phosphorus dopants is dramatically improved.