Preparation Of Composite Polymer Micelles As Controlled Carrier

Polymeric complex micelles,which were synthesized by introducing more than one kind of polymer blocks with different properties into the same micelle,have a complex core or shell and would match well with the higher requirement of drug release and catalyst carrying.In this thesis,many kinds of complex micelles were designed and synthesized through the hydrogen bonding and/or the electrostatic interactions between differene polymer blocks.The complex micelles were used to control the release velocity of the encapsulated drug and to madulate the catalytic activity of the loaded metallic nanoparticles.The contents of the corresponding research works are shown as follows.Novel kind of worm-like complex micelles were synthesized through the hydrogen bonding between PAA block and P4VP block by adding poly(N-isopropylacrylamide)-block-poly(4-vinylpyridine)(PNIPAM-b-P4VP) into the solution of poly(ethylene glycol)-block-poly(acrylic acid)(PEG-b-PAA) in ethanol.The resulted micelles have a PAA/P4VP complex core and a PEG&PNIPAM mixed shell.The length of worm-like aggregates could be adjusted by changing the weight ratio of W_{(PNIPAM-b-P4VP)}/W_(PEG-b-PAA).The terminal group of the aggregates is "living".The newly added PNIPAM-b-P4VP chains would grow onto the aggregates from the group and acted as a bridge to connect two aggregates, and the length of the micelles increased.Multilayered micelles was synthesized through the electrostatic interaction and the hydrogen bonding between PAA block and P4VP block using the layer by layer assembly method by adding PNIPAM-b-P4VP and PEG-b-P4VP into the polystyrene-block-poly(acrylic acid)(PS-b-PAA) micellar solution.The corona of the micelles consisted of a kind temperature sensitive polymer block and a kind of pH sensitive polymer block.The multi-layered morphology would not change when the micelles were transferred into water.The micelles have both pH and temperature sensitivity.PNIPAM would collapse onto the PAA/P4VP complex layer when the solution was heated above LCST,and the excessive P4VP chains would still extend into the solution.Accordingly,a kind of reverse micelles formed.PS-b-PAA spherical micelle with a liquid core and PAA shell were prepared with the assistance of 1,2-dichloroethane.In the process of adding the mixture of PNIPAM-b-P4VP and PEG-b-P4VP,multi-layered micelles with mixed corona consisted of both PNIPAM and PEG chains were constructed through the electrostatic interaction and hydrogen bonding between PAA block and P4VP block. When heating above LCST,PNIPAM chains collapsed onto the PAA/P4VP complex layer while PEG chains still stretched into the solution through the collapsed PNIPAM layer,leading to the formation of hydrophilic channels around PEG chains. The ratio of the channels in the corona of the micelles can be modified by changing the weight ratio of W_{(PNIPAM-b-P4VP)}/W_(PEG-b-P4VP),and accordingly,the release velocity of the drugs encapsulated in the hollow space can be controlled through this method.Polymeric micelles with a PS core,PAA/P4VP complex shell and PEG&PNIPAM mixed corona were synthesized through the layer by layer assembly method and used as the supporter for the gold nanoparticles(GNs).When heated above LCST,PNIPAM would collapse onto the PAA/P4VP complex layer,acting as a barrier for the diffusion of small molecules and also preventing the sheeding of the GNs.Hydrophilic channels around PEG chains formed when PNIPAM chains collapsed above LCST.The ratio of the channels in the corona can be tuned by changing the weight ratios of PEG chains to PNIPAM chains in the corona and the catalytic activity of the GNs can be modulated by the channels.This concept of constructing the hydrophilic channels in the corona while the micelles were stabilized by the extended PEG chains can be further used in controlled drug delivery, DNA transfer and gene therapy.Hollow crosslinked polymers(HCPs) were synthesized using arm first method via atom transfer radical polymerization.The polymerization process was performed in mini-emulsion system,in which the macro initiators,PEG-Br and PNIPAM-Cl, were in the water phase whileas the vinyl-monomer,4VP,and the cross-linker,DVB, were in the butanone phase.The resulted polymer contained a hollow space,and the volume of the hollow space could be adjusted by changing the ratio of water to butanone.There were two kinds of arms,PEG and PNIPAM,in the polymer,and their ratio can be well controlled.