Synthesis And Application Of Tadpole-Shaped Block Polymers And Multifunctional Polymer-Based Modification Reagents

As the hot research fields in today’s materials science,especially in functional polymer materials,the study of the structure and function of responsive polymers and hybrid nanoparticle based on polymerization has exhibited important role in the development of information technology,materials science and nanotechnology.Meanwhile,there are still a large number of scientific problems that need to be explored.As we all know,the structure of polymer has a great influence on the performance.For instance,the performance of ring and tadpole shape polymers is different from the linear polymers.Because of the difficulty in the synthesis of polymers with complex topological structure,the study of theoretical and application has been limited.Compared to traditional inorganic nanoparticles,hybrid nanoparticles based on polymerization possess many special performances which has attracted the attention of a large number of researchers.Hybrid nanoparticles are usually synthesized in organic phases,while hybrid nanoparticles are mostly used in aqueous solutions.Hence there is a need for the development of highly effective modified reagents.This paper focused on the preparation of tadpole-shaped temperature-sensitive block polymers and the properties in aqueous solutions,designed and synthesized a multifunctional modified reagent to modify hybrid nanoparticles.This dissertation can be further categorized into two main parts as described below:1.We report on a method for reducing the hydrodynamic radius,<Rh>,via Atom Transfer Radical Polymerization(ATRP)and click chemistry.Well-defined thermo-responsive tadpole-like block copolymers,PEG-b-cyclicPNIPAM,were synthesized via ATRP and click reactions.Firstly,ATRP initiator,PEG45(-alkynyl)-Br,was used to initiate N-Isopropyl acrylamide(NIPAM)to thermos-sensitive block polymer of PEG45(-alkynyl)-b-PNIPAM-Br with a alkynyl at the terminal of PEG chain and a halogen group at the terminal of PNIPAM chain.Then,the halogen group was modified into azide group with sodium azide.Finally,the PEG45-b-cyclicPNIPAM was prepared with click chemistry in which the alkynyl and azide group occurs cyclization.We found that the PEG-b-cyclicPNIPAM52 in aqueous systems displayed micellization in the process of heating.And when above the phase transition temperature,the hydrodynamic radius,<Rh>,of PEG45-b-cyclicPNIPAM52(tadpole-like structure,41nm)was obviously much smaller than PEG45(-alkynyl)-b-linearPNIPAM52-Br(linear structure,85nm).The same phenomena was also found when the degree of polymerization of PNIPAM was 110.In brief,it may be a good approach to reducing the<Rh>of micelles by modifying the polymers with cyclization.The polymers with small<Rh>can be good candidates as passive targeting drugs clinically.2.Amphiphilic block polymer,PEG-b-P(SS-co-SiDA),which containing both lipoic and dopamine groups,was prepared from Alkynyl-SS and NH2-SiDOPA.Then the block copolymer was used to modify hydrophobic gold,iron oxide nanoparticles and quantum dots to make them water-soluble nanoparticles.These water-soluble nanoparticles are characterized by electron microscopy and ultraviolet/visible absorption spectra:PEG-b-P(SS-co-SiDA)can modify gold,iron oxide nanoparticles and quantum dots from hydrophobic to water-soluble by ligand exchange efficiently.Moreover,the reagent can also modify the gold particles and iron oxide particles simultaneously to form a complex with certain structure.