Synthesis, Self-Assembly Of Amphiphilic Hyperbranched Supramolecular Block Copolymers

Supramolecular chemistry is the chemistry of the intermolecular bond, covering thestructures and functions of the entities formed by association of two or more chemicalspecies. The intermolecular bond includes hydrogen bonding, metal coordination,hydrophobic forces, van der Waals forces, π-π interactions and electrostatic effects.Supramolecular chemistry has become a exciting and promising research field ininterdisciplinary subject of physics, chemistry, biology, materials science, as well as lifescience. Supramolecular polymer is an important branch of supramolecular chemistry inthe field of polymer chemistry. Hyperbranched polymer is also an important branch ofdendritic polymers which has a large amount of terminal functional groups and manyinner cavities. In this dissertation, based on the review and summarization of previousoutstanding research works of supramolecular polymer and self-assembly ofhyperbranched multiarm copolymers, supramolecular host-guest interaction was used toconstruct hyperbranched block polymer. Hyperbranched polymers with multiple kinds ofmono-reactive focal point were synthesized, the host-guest complexation between focalpoints was utilized to couple the hydrophobic hyperbranched polymer with hydrophilichyperbranched or linear polymer, and then the amphiphilic hyperbranched supramolecularpseudo block copolymers were obtained. Subsequently, the self-assembly and disassemblybehaviors of them were investigated. In addition, the hyperbranched-hyperbranched andlinear-hyperbranched copolymers based on covalent bond were synthesized, theself-assembly behaviors in selected solvent of them were investigated. The main resultsare shown as follows. 1. Synthesis and its photo-responsive self-assembly behavior of Janus amphiphilichyperbranched-hyperbranched supramolecular pseudo block copolymer.Hydrophobic hyperbranched poly3-ethyl-3-oxetanemethanol with azobenzene asfocal point （AZO-g-HBPO） and hydrophilic hyperbranched polyglycidol withcyclodextrin as core （β-CD-g-HPG） were synthesized according to the cationicring-opening polymerization and oxyanionic ring-opening multibranching polymerization,respectively. The recognization of cyclodextrin and azobenzene was achieved by addingselected solvent to common solvent, and then, Janus amphiphilic hyperbranched-hyperbranched supramolecular pseudo block copolymer was obtained. After dialysisagainst water, the self-assembly of supramolecular polymer completed. DLS and2DNOESY were used to track the formation and self-assembly process of Janussupramolecular copolymer, the results demonstrated the complexation of cyclodextrin andazobenzene. TEM, SEM, Cryo-TEM and AFM were used to directly detect themorphology of the self-assembly objects. The results indicated that the supramolecularcopolymer self-assembled into vesicle with narrow size distribution in water, the thicknessof the vesicle wall was about9.6±0.6nm which is equal with double length of Janussupramolecular copolymer. The vesicles may possess a bilayer structure with twohydrophilic HPG shell layers and one hydrophobic HBPO core layer. Adding competitivehost or guest moleculars with a stronger complexation capacity and irradiation with UVlight with365nm were used to investigate the stability and the disassembly behaviour ofsupramolecular vesicle. The results show that the supramolecular viescle was stable withcompetitive host or guest moleculars and heating, disassembled with irradiation of UVlight with365nm. In addition, the details of the self-assembly process as well as thevesicle structure have been disclosed by a dissipative particle dynamics （DPD） simulation.2. Synthesis and its electrochemical-responsive self-assembly behavior of Janusamphiphilic hyperbranched supramolecular pseudo block copolymersHydrophobic hyperbranched poly3-ethyl-3-oxetanemethanol with ferrocene as focalpoint （Fc-g-HBPO） was synthesized according to the cationic ring-opening polymerization.Hydrophilic end-capped polyethylene oxide with β-cyclodextrin （β-CD-g-PEO） wassynthesized according to the mono-6-deoxy substitution of β-cyclodextrin. Combined withβ-CD-g-HPG in the first part, Janus amphiphilic hyperbranched-hyperbranched andlinear-hyperbranched supramolecular pseudo block copolymers were obtained by recognization between cyclodextrin and ferrocene. After dialysis against water, theself-assembly of supramolecular polymers completed. DLS and2D NOESY were used totrack the formation and self-assembly process of supramolecular copolymers, the resultsdemonstrated the complexation of cyclodextrin and ferrocene. TEM and SEM were usedto directly detect the morphology of the self-assembly objects. The results indicated thatthe supramolecular copolymers self-assembled into vesicle in water. Adding competitivehost or guest moleculars with a stronger complexation capacity, chemical andelectrochemical oxidation were used to investigate the stability and the disassemblybehaviour of supramolecular vesicles. The results show that the supramolecular vesicleswere stable with competitive host or guest moleculars, chemical and electrochemicaloxidation. The supramolecular vesicles disassembled after adding electrolyte to thesupramolecular system after electrochemical oxidation.3. Synthesis of Janus amphiphilic linear-hyperbranched supramolecular pseudo blockcopolymer and its photo controlled self-assembly and morphology transformation fromvesicles to lamellar structure and fibers.Hydrophobic hyperbranched poly3-ethyl-3-oxetanemethanol with yne group as focalpoint （YNE-g-HBPO） was synthesized according to the cationic ring-openingpolymerization. Janus type amphiphilic hyperbranched polymer （β-CD-g-HBPO） wasobtained after click reaction between YNE-g-HBPO and mono-6-deoxy-6-azide-β-cyclodextrin. Polyethylene oxide end-capped with azobenzene （AZO-g-PEO） wassynthesized using4-（Phenylazo）benzoic acid and methoxypolyethylene glycol as rawmaterials. Interestingly, the amphiphilic β-CD-g-HBPO and AZO-g-PEO self-assembledto lamellar structure and fiber respectively. The amphiphilic linear-hyperbranchedsupramolecular pseudo block copolymer was obtained by recognization of cyclodextrinand azobenzene. After dialysis against water, the self-assembly of supramolecularpolymers completed. DLS and2D NOESY were used to track the formation andself-assembly process of Janus supramolecular copolymer, the results demonstrated thecomplexation of cyclodextrin and azobenzene. TEM, SEM were used to directly detect themorphology of the self-assembly objects. The results indicated that the supramolecularcopolymer self-assembled into vesicle in water. UV light with365nm was used toinvestigate the stability and the disassembly behaviour of supramolecular vesicles. Theresults show that the supramolecular vesicles disassembled into lamellar structure and fibers. They could reversibly assemble into vesicle under the irriadiation of visible light.4. Synthesis and self-assembly of amphiphilic hyperbranched-hyperbranched andlinear-hyperbranched copolymers based on covalent bond;Hydrophilic hyperbranched polyglycidol with azide group as focal point （N₃-g-HPG）was synthesized according to the oxyaionic ring-opening polymerization using3-azidopropan-1-ol as initiator. Janus amphiphilic hyperbranched-hyperbranched blockcopolymer （HBPO-b-HPG） was obtained after click reaction between N₃-g-HPG andYNE-g-HBPO mentioned in the former part. DLS, SEM and TEM were used toinvestigate the self-assembly of HBPO-g-HPG in selected solvent. The resultsdemonstrated that Janus amphiphilic block copolymer self-assembled into vesicles ingboth water and THF. In addition, Janus amphiphilic linear-hyperbranched blockcopolymer （HBPO-b-PEO and HBPO-b-PEO-b-HBPO） were synthesized usingmethoxypolyethylene glycol and polyethylene glycol as initiator through cationicring-opening polymerization. The self-assembly behaviours of them were also discussed atthe same time.