| Abstract
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Amphiphilic hydrogels with different molecular architecture were successfully synthesized by two methods: (1) Williamson ether synthesis with linear or hyperbranched poly [(p-chloromethyl) styrene], PPCMSt and poly(ethylene glycol), PEG, and (2) nucleophilic substitution reaction between PPCMSt and poly(oxyalkylene) diamine, Jeffamine. Highly porous networks were achieved, as confirmed by scanning electron microscopy (SEM), exhibiting high swelling ratio in both water and organic solvents. Dynamic swelling studies showed that the networks absorb water quickly and reach equilibrium in 1-3 hours. Reactive amphiphilic hydrogels with covalently bonded drugs were prepared by the same methods using the drug modified PPCMSt. Preliminary drug release study using model compounds demonstrated the kinetics of drug release in terms of the physical properties of drugs, the microstrucutre of polymer matrix, the drug-polymer interaction, and more particularly, the hydrolysis of ester linkage between the drug and polymer. Furthermore, original nanoparticles consisting of a hydrophobic core (PPCMSt), linked with a biocompatible hydrophilic shell (PEG), were prepared in aqueous media by self-assembly of comb and star-like amphiphilic block copolymers. These two copolymers were synthesized by grafting the alkyne mono-terminated PEG chains with different molecular weight to the linear PPCMSt backbone or hyperbranched PPCMSt via Huisgen cycloaddition. The physical properties of block copolymers were controlled by the nature of the two building blocks, the architecture of macromolecules, and the molecular weight of PEG. By modification of the surface functionalities with various compounds, these nanoparticles can be developed to serve as unique drug-delivery vehicles that have the ability to respond to ambient changes including pH and temperature. Key words. hyperbranched polymer, amphiphilic hydrogel, swelling, morphology, block copolymer, micelle, click chemistry.
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