Construction Of Dual-responsive Supramolecular Topological Polymers And Preparation Of Functional Self-assemblies

Supramolecular topological polymers（STP）not only possess the unique chemical and physical properties but also the dynamic tunable character of supramolecular chemistry,which may have potential applications in various fields,such as biomedicine,smart materials and sensing detection.Up to now,the research on the STP is mainly focused on the construct methods and aqueous self-assembly behaviors.However,research on the mechanism and the dynamic process of the self-assembly behaviors are still limited.In addition,the use of the STP with unique chemical and physical properties for various applications is still a challenge.In this study,a series of supramolecular star polymers,supramolecular hyperbranched polymers and the corresponding supramolecular assemblies were designed and synthesized.The relationship between properties and structures of the polymers and the potential applications of supramolecular assemblies in smart drug delivery/control release and sensing detection were emphasize investigated.The main contents and results are summarized as follows:Firstly,the ultrasound/light or ultrasound/redox dual-responsive self-assembly and the drug control release behaviors based on host-guest-conjugated amphiphilic molecules were studied.Two AB₂ type host–guest-typed amphiphilic molecules Azo-CD₂ and Fc-CD₂ were designed and synthesized through click chemistry.They self-assembled into spherical aggregates without external stimuli,and then transformed to bigger supermolecular hyperbranched self-assemblies（SHPS）induced by ultrasound in aqueous solution.These SHPS could be further dissociated into small branched or spherical aggregates under UV light irradiation or H₂O₂ treatment,whereas reverted to SHPS again by visible light irradiation or GSH treatment.By utilizing the above ultrasound and photo or redox-dually tuned self-assembly morphology transition features,programmed drug delivery behavior was observed through the cumulative release curves of doxorubicin（DOX）-loaded self-assemblies.Furthermore,utilizing the host–guset chemistry on the basics of the surface CD groups,the Fc-CD₂ spherical self-assemblies can be further modified by lactobionic acid-terminated PEG,which can form a novel multifunctional self-assemblies for targeted delivery and smart control release.Secondly,two thermo and photo responsive Y-shaped supramolecular polymer,PNIPAM-2CD/2（Azo-mPEG）（SSP2）with two adjacentβ-cyclodextrin/azobenzene（β-CD/Azo）binding sites,and another SSP PNIPAM-CD/Azo-2mPEG（SSP1）with similar building blocks,but only oneβ-CD/Azo binding site as a control,are designed and synthesized.Host–guest binding-site-tunable self-assembly of stimuli-responsive supramolecular polymers was then investigated.Upon gradually increasing the polymer solution temperature or irradiating with UV light,SSP2 self-assemblies with a higher binding-site distribution density;exhibits a flower-like morphology,smaller size,and more stable dynamic aggregation process;and greater controllability for drug-release behavior than those observed with SSP1 self-assemblies.The host–guest binding-site-tunable self-assembly was attributed to the positive cooperativity generated among adjacent binding sites on the surfaces of SSP2 self-assemblies.Host-guest chemistry is exploited to tune the rate at which block copolymer vesicles undergo morphological transitions.A concentrated aqueous dispersion of poly（glycerol monomethacrylate-co-glycidyl methacrylate）-poly（2-hydroxypropyl methacrylate）[P（GMA-co-GlyMA）-PHPMA]diblock copolymer vesicles was prepared via polymerization-induced self-assembly（PISA）.The epoxy groups in the GlyMA residues were ring-opened using a primary aminefunctionalizedβ-cyclodextrin（NH₂-β-CD）in order to prepareβ-CD decorated vesicles.Addition of azobenzene-methoxypoly（ethylene glycol）（azo-mPEG）to such vesicles results in specific binding of this watersoluble macromolecular reagent to theβ-CD groups on the hydrophilic P（GMA-co-GlyMA）stabilizer chains.Binding of a water-soluble azo-mPEG analyte to such vesicles leads to a significantly faster change in copolymer morphology compared to theβ-CD-functionalized vesicles alone.Moreover,the rate at which such morphological transitions occur can be further fine-tuned via UV/visible-light irradiation or the use of competitive guest molecules.Finally,we report the first example of switching the switch with a completely“off-on”/“on-off”conversion via the phototunable upper critical solution temperature transition of the binary/ternary supramolecular host-guest system for use as a laser sensor device for detecting temperature changes.A binary supramolecular system（β-cyclodextrin trimer（β-CD₃）/double azobenzene-terminated polyethylene glycol oligomer（Azo-PEG-Azo））was constructed.This binary supramolecular system has a special switching device with a completely“off-on”mode by varying the UV/visible light irradiation.As the sample solution temperature decreases,the reversible UCST phase transition occurs,and the supramolecular switch remains in the“on”state.However,when the preliminary sample solution was irradiated by UV light above the UCST,the supramolecular switch can be completely held in the“off”state,resulting from the disappearance of the UCST transition even though the solution temperature decreased.With visible light irradiation,the“on”function of the supramolecular switch can be recovered again.Additionally,to confirm this supramolecular switching property,another ternary supramolecular system based onβ-CD₃/double naphthalene-terminated PEG（NP-PEG-NP）/single azobenzene-terminated polyethylene glycol monomethylether（mPEG-Azo）was constructed,and this system exhibited an“on-off”supramolecular switch function based on a similar UCST-type phase transition.The smart supramolecular switch as a novel laser sensor device was used to detect temperature changes through an“off-on”or“on-off”mode.