| Self-assembly widely exists in biological cells as a process to form complex orderlysupramolecular aggregates, such as lipid membranes, proteins, nucleic acids, etc.Molecular self-assembly is a method with which molecules or parts of moleculesspontaneously form micelles by non-covalent bond interaction, such as van der Waalsforce, coulomb force, hydrophilic and hydrophobic function, π-π interaction, etc.Self-assembly is a kind of effective and simple method to get ordered materials suchas molecular crystals, crystal structure, and semicrystalline macromolecule. Therefore,molecular self-assembly plays an irreplaceable role in chemistry, physics, life science,materials science, nanotechnology and other fields.Poly (aryl ether ketone)(PAEKs) has excellent physical and chemical properties,such as good temperature resistance and mechanical performances, etc., so it has beenwidely used in the fields of aerospace, electronics, and nuclear power. However, at thesame time, PAEKs with linear molecular structure has disadvantages which limit theirapplications, for instance, the high melt viscosity, poor solubility and processingdifficulties. Hyperbranched poly (aryl ether ketone)(HPAEKs) have the samechemical composition with linear poly (aryl ether ketone), and the difference is thehyperbranched three-dimensional ellipsoidal stereo structure. In comparison withlinear PAEKs, HAPEKs have better solubility and lower melt viscosity and there aremany functional groups at the end of the molecular chains to be modified. Theseadvantages not only make up the defects of linear PAEKs mentioned above, but alsobroaden the application fields of PAEKs.The self-assembly study is traditionally based on amphiphiles with low molecular weight, dendrimers and linear copolymers. All kinds of polymer micelles with variousmorphologies have been obtained using self-assembly, such as microspheres, vesicles,nano-ribbons, films, fibers, tubes etc. Hyperbranched polymers, consisting ofbranched units, linear units and terminal units, don’t possess the perfect molecularstructure as dendrimers. But due to their unique properties, hyperbranched polymershave more application value. Amphiphilic hyperbranched PAEKs has thecharacteristics of molecular structure and unique properties of hyperbranchedpolymers, and the hydrophilic and hydrophobic segments, so they can be excellentprecursors for self-assembly.Much attention has been paid in the research of the self-assembly of copolymerscontaining rod polymer or oligomer segments to acquire functional materials withdifferent supramolecular structures both in solution and solid. However, the rigidmoieties of rod-coil block copolymers reported in the literatures were mainly focusedon linear rod polymers or oligomers, which included thiophene, phenylene, quinolone,fluorene, etc. In this paper, we mainly investigate the self-assembly of amphiphilichyperbranched poly (aryl ether ketone)-poly (ethylene glycol) copolymers insolution.First of all, we synthesized hydroxyl-terminated hyperbranched poly (aryl etherketone)(OH-HPAEK), then grafted activated PEG with different molecular weightand content onto OH-HPAEK. The molecular structure, the number-averagemolecular weight and the thermal properties of HPAEK-graft-PEG were confirmedand characterized.The results of self-assembly investigation demonstrated that the hyperbranchedrod-coil diblock copolymer (HPAEK-graft-PEG) with ill-defined molecular structurecould self-assemble into regular microspheres with obvious core-shell structure inwater/tetrahydrofuran (THF) mixture, and the diameter of the microspheres could beeasily controlled by just adjusting the initial concentration of the copolymer in thecommon solvent of THF. The heat-treated experimental results demonstrated that thepolymer microspheres possessed excellent thermal property which could stably existeven if heated at130oC for10h. However, when we changed the polarity of the selective solvents and the molecularweight of the PEG chains, polymer micelles with various morphologies wereobtained.Finally, we discussed the mechanism of the formation of microspheres, othernano-scale objects and the reason that control the diameter of the spherical micelles.This work established a base for which this kind of material will be researchedfurther. |
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