Fabrication Of Responsive Polymeric Assemblies And Functional Materials

Stimuli-responsive polymers have been applied in many fields like chemical sensors.The supramolecular self-assembly of stimuli-responsive amphiphilic polymers and hybrid nanoparticles are the hottest topics in material science.Although sciencists have made great breakthroughs and innovations in the field of material science,there are still many scientific problems that need to be solved by humans.This dessertation mainly focuses on fabrication of polymer/inorganic hybrid asymmetric nanoparticles,polymer-based oxygen sensitive sensors,and signal self-amplification nanoreactors based on hydrogen peroxide(H2O2)responsiveness.The dissertation can be categorized into the following three parts:1.Fabrication of small sized Janus hybrid nanoparticles remains challenging.We report on a highly efficient and simple method to fabricate small sized Janus hybrid gold nanoparticles by ligand exchange reaction.The temperature-sensitive star polymers((LA)7-CD-(PNIPAM)14)are fabricated based on ?-cyclodextrin(?-CD)by combining Atom Transfer Radical Polymerization(ATRP)and click chemistry.The secondary hydroxyl groups of ?-CD are modified into ATRP initiators which initiate polymerization of N-isopropyl acrylamide(NIPAM)to form fourteen thermal-sensitive PNIPAM chains.Then,asymmetrically functionalized star polymers(LA)7-CD-(PNIPAM)14 were prepared by modifying primary hydroxyl groups of ?-CD into azide groups and then coupling seven 5-(1,2-dithiolan-3-yl)-N-(prop-2-ynyl)pentanamide molecules by click chemistry.The amphiphilic Janus hybrid gold nanoparticles Au-CD-(PNIPAM)14 were prepared by the polymeric ligand(LA)7-CD-(PNIPAM)14 undergoing ligand exchange with n-butylthiol on the surface of gold nanoparticles.Similar to amphiphilic block copolymers,the prepared amphiphilic hybrid nanoparticles Au-CD-(PNIPAM)14 could self-assemble into supermicelles in water.2.Difluoroboron dibenzoylmethane-polylactide(BF2dbm-PLA)exhibits both fluorescence and room temperature phosphorescence(RTP).We hypothesized that RTP phenomenon of difluoroboron dibenzoylmethane(BF2dbm)may be present in amorphous polymers.The copolymers were obtained by copolymerizing BF2dbm(R)-AE with styrene,methacrylate or acrylamide monomer,respectively.The experimental data indicate that all of these polymers exhibit oxygen-sensitive RTP phenomena,so these polymers have many advantages over existing materials on fabrication of various types of oxygen sensors.3.Amphiphilic block copolymers PEO45-b-PNBMA15 can self-assemble into vesicles.Based on the H2O2 responsive vesicles,we construct nanoreactors with a positive feed-back property.Glucose oxidases are encapsulated in hydrophilic cavity of the vesicles.Glucose diffuses into the hydrophilic cavity of the vesicles catalyzed by GOx to generate H2O2 which can trigger decaging reactions to release primary amine moieties.As a consequence,prominent amidation crosslinking reaction then occurs associated with hydrophobic-to-hydrophilic transition in the vesicle bilayers.During the period of inducement the difusion of glucose into the cavity is relatively slow because of the hydrophobicity of the vesicle bilayers.After the inducement period,the rate of diffusion of glucose into the vesicle cavity is accelerated due to the increased permeability of the vesicle bilayer.Meanwhile,H2O2 is further increased by enzyme catalyzed reaction,continuing to trigger the decaging reactions to increase the permeability of the vesicle bilayers.Therefore,a positive feedback process is formed.