Study Of Multifunctional Hybrid Co-assemblies Based On Poly(ether Amine)s

Self-assembly is omnipresent throughout daily life and nature,which ranging from galaxy formed by stars to membranes of living cells formed by phospholipids.As one part of self-assembly,co-assembly based on polymer and inorganic nanoparticles have attracted many attentions in recent decades.The obtained co-assemblies possess both the unique properties such as thermal,magnetic,optics,and mechanical property of inorganic nanoparticles and the processibility,biocompatibility,and stimulative responsibilities of polymers,and the hybrid co-assemblies may have other properties different with the polymer or nanoparticles for the synergistic effect.These interesting properties make the hybrid assemblies potential applications in smart materials,nano-sensors,and optoelectronic devices.Recently,our group has developed a novel series of multi-responsive hyperbranched poly?ether amine?s?hPEAs?via the click reaction between amino groups and epoxy monomers.The reaction is atom economic and the condition is mild.The hPEAs possess a large number of secondary amino groups in the periphery and a large number of hydroxyl groups on the backbone.Through the sequential functionalization of hPEAs,different functional moieties can be introduced to the periphery and backbone of hPEAs to obtain amphiphilic hPEAs with desired properties.By choosing different functional groups which have strong interactions with nanoparticles?NPs?,multi-stimuli responsive hybrid assemblies based on co-assembly of hPEAs and NPs can be achieved.We have prepared various hybrid assemblies based on hPEAs and nanoparticles?Fullerene and Polyhedral Oligomeric Silsesquioxane?.Furthermore,dynamically control of the morphologies and the distribution of the nanoparticles in assemblies are also achieved.The contents of this thesis are listed as follow:?1?A novel multi-responsive fluorescent nanorod was fabricated through the versatile co-assembly of fullerene C₆₀ and anthracene-ended hyperbranched poly?ether amine??hPEA-AN?.The size of the obtained nanorods is 2-12?m in length and 50-90 nm in diameter while can be tuned by the feed ratio.The supramolecular nanorods(C₆₀@hPEA-AN)can be further cross-linked through photodimerization of anthracene to enhance the stability.C₆₀@hPEA-AN nanorods are amphiphilic,responsive,and fluorescent.The fluorescence of C₆₀@hPEA-AN nanorods in aqueous solution is responsive to temperature and pH.Furthermore,the nanorods exhibit interesting temperature-enhanced fluorescence.Detailed fluorescence study revealed that the temperature-enhanced fluorescence behavior of C₆₀@hPEA-AN nanorods might be ascribed to the static quenching of anthracene by C₆₀.?2?A novel series of core-shell microspheres?CSM?was fabricated from co-assembly of anthracene ended hyperbranched poly?ether amine??hPEA-AN?and anthracene containing polyhedral oligomer silsesquioxane?POSS-AN?.The shell of the obtained CSM is comprised of hPEA-AN,while POSS-AN prefers the crystallized aggregation in the core.With the increasing content of hPEA-AN in the coassembly,the diameter of CSM decreased from 930to 616 nm,while the thickness of shell increased from 95 to 170 nm.Detailed FL and UV-vis tracing showed that the strong?-?interaction is the key to form these uniform CSM.The obtained CSM can be further cross-linked through photodimerization of anthracene to enhance the stability.Moreover,polymeric hollow microspheres?PHM?were prepared by removing the POSS-AN core of CSM by hydrofluoric acid?HF?.The obtained PHM are amphiphilic and fluorescent,and responsive to environmental stimulis such as temperature and pH.PHM can be used in the encapsulation and controlled release of guest molecules.Moreover,the controlled release of guest molecules from PHM can be monitored by its own fluorescence change.?3?Dynamic control of the location of NPs in a restricted space was realized via the thermal annealing of CSM,and the immigration of NPs was clearly observed by TEM.Detailed study has shown that,the core-shell structure of CSM is a meta-stable structure,and may convert to homogenous structure at certain condition.Actually,when heated above the melt point of POSS-AN,the crystalline structure is destroyed and immigration between core and shell took place.Upon thermal annealing at a temperature higher than the melting point of POSS-AN,the diffusion of POSS-AN from the core to the shell of CSM leads to a transition of morphology from the core–shell structure to core–transition–shell to the homogeneous morphology,which has been revealed by experimental results of TEM and DSC.The mechanism for the morphology transition of CSM induced by the diffusion of POSS-AN was disclosed by both Fick's law of diffusion and dissipative particle dynamics?DPD?simulation,both of which fit well.Furthermore,when the temperature dropped below the melt point,immigration stops.The transitional morphologies can be further locked by the photodimerization of AN moieties.Additionally,the distribution of NPs can also be predicted by Fick's law,thus the spatial distribution of POSS in the microspheres can be controlled dynamically by tuning the temperature and time of thermal annealing.?4?A novel class of core-shell microsphere is fabricated via co-assembly of amphiphilic azobenzene-ended hyperbranched poly?ether amine??hPEA-AZO?and the inorganic azobenzene containing polyhedral oligomeric silsesquioxanes?POSS-AZO?.The azobenzene moiety may take a trans-to cis-isomerization under UV light which will affect the size and amphiphilicity of the assemblies.According to the previous study,the core-shell structured morphology is captured by the crystallized aggregation of POSS in the core during the co-assembly of POSS-AZO and hPEA-AZO.Azobenzene is an ideal component for the study of morphology transformation:on one hand,the photo-thermal effect may destroy the crystal core;on the other hand,the photo-isomerization effect may change the core size and Hydrophilic-Lipophilic balance.Detailed study has shown that,upon annealing at 365 nm,the morphology of assemblies transformed from core-shell to composite vesicle to vesicles.Further study also showed that the time of UV irradiation,the polarity of solvent,and the backbone of hPEA may also affect the morphology transition process.This approach might provide some guidelines in designing and preparing hybrid co-assemblies with the fantasy morphologies.