最新刊期
卷 37 ， 期 2 ， 2017
- 摘要：Molecular design and controllable preparation of hyperbranched polymers are of great significance for their industrialized application, which depends on the understanding for their formation mechanism. At the end of 1980's, Kim et al. successfully prepared hyperbranched polyphenylenes. Since then, the hyperbranched polymers have been a hot topic in polymer science and great progress has been made in both experiments and theory. The topological structure and molecular parameters can be estimated by the theory of hyperbranched polymers, which provided a great help to the molecular design and controllable preparation of hyperbranched polymers. Among the various theoretical models, kinetics of hyperbranched polymerization is the most perfect due to the clear principle and rigorous derivation, by which the analytical expressions of the molecular weight distribution functions and the various molecular parameters of the products can be derived. It is one of highlights of scientists working in China. The polymerization of ABg type monomer is one of the most important technologies to prepare the hyperbranched polymers. However, the molecular weight distribution is extremely wide for the products of the polycondensation with pure ABg type monomer. The presence of a little of multifunctional group can narrow the molecular weight distribution. Moreover, the polydispersity of hyperbranched polymers obtained can drastically decrease when the monomers are slowly added to the reaction system. Another deficiency of the hyperbranched polymers resulted from the polycondensation with pure ABg type monomer is the poor mechanical properties. One of the improved approaches is the copolymerization of AB and ABg monomers, in which some linear segments can be incorporated into the hyperbranched polymer obtained. Thus, the degree of branching and the mechanical properties of the polymer can be designed by suitable monomer feed ratio. Taking account of the substitution effect, various degree of branching of the products also can be understood. Yan et al. developed kinetic model for a large variety of hyperbranched polymerizations and successfully explained these phenomena mentioned above. In this work, the early Flory-Stockmayer theory for hyperbranched polymers is reviewed and, specially, the kinetic theory of hyperbranched polymerization with ABg type monomer is introduced.关键词：Hyperbranched polymer;Polymerization kinetics;Molecular weight function;Degree of branching
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发布时间：2021-05-18 - 摘要：Dendritic molecules are a class of highly branched macromolecules and/or polymers having a three-dimensional, nanosized globular architecture with intramolecular cavity and numerous surface functional groups. These unique structural features can endow dendritic molecules with a lot of particular and interesting functionalities and photophysical properties, making them very attractive in many areas including chemistry, biology, materials, and so on. In the past 30 years, organic/polymeric second-order nonlinear optical (NLO) materials have been widely investigated due to their great potential in telecommunications, computing, terahertz generation, detection, and many other photonic applications. So far, one of the major challenges encountered in this field is how to translate high molecular nonlinearities (μβ) of chromophores into large macroscopic material nonlinearities (i.e. second harmonic generation coefficient, d33) efficiently, due to the strong intermolecular dipole-dipole interactions between chromophore moieties, which can make their poling induced noncentrosymmetric alignment a daunting task. According to the site-isolation principle, the dendritic structure has been well-recognized as the next generation molecular topology to modify chromophores into the ideal spherical shape that can minimize the dipole-dipole interactions significantly to improve the poling efficiency. From 2006, our group has done many systematic researches in this field with an attempt to better understand the structure-properties relationship of NLO polymeric materials. In this review, after a brief introduction of dendritic molecules and second order nonlinear optics, we will summarize our recent research work on second order NLO polymers with dendritic structure, including high generation dendrimers, hyperbranched polymers and dendronized hyperbranched polymers (a new polymer model combining hyperbranched polymer and dendrimer). We mainly focus on the discussion how to rationally design and tailor the topological structures of the dendritic NLO polymers that can significantly enhance their comprehensive material performance through several molecular design strategies such as "suitable isolation group", "isolation chromophore" and the Ar-ArF self-assembly. Finally, a short outlook for future opportunities in advancing this field is also presented.关键词：Dendritic polymers;Nonlinear optics;Topological structure;Dendronized hyperbranched polymer
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发布时间：2021-05-18 - 摘要：Hyperbranched polymers, as one kind of three dimensional macromolecules with globular and dendritic architectures, have unique properties of good solubility, low viscosity, topological structure, a lot of functional groups, etc. Over the past decades, the hyperbranched polymers have attracted more and more attention and been widely applied in diverse areas including coatings, additives, biomaterials, supramolecular chemistry, nanoscience and technology, photoelectricmaterials, and so on. Click polymerization with the advantages of facile monomers accessibility, mild reaction conditions and high reaction efficiency has been developed into a sort of powerful polymerization tool for the synthesis of polymers with well-defined molecular structures and advanced functional properties. This method has also been extensively used in the synthesis of hyperbranched polymers. This review mainly summarizes the progress on the synthesis of the hyperbranched polymersvia alkyne-based click polymerizations in the last 5 years. The Cu (Ⅰ)-catalyzed azide-alkyne click polymerization could readily produce 1, 4-regioregular hyperbranched polytriazoles, whereas the Ru (Ⅱ)-catalyzed azide-alkyne click polymerization could generate 1, 5-regioregular hyperbranched polytriazoles. Meanwhile, the azide-alkyne click polymerizations under metal-free conditions were also developed through the ingenious design of monomers. Metal-free click polymerization of activated alkyne and azide monomers could efficiently produce hyperbranched polytriazoles with fraction of 1, 4-isomers up to 91.7%. The obtained polytriazoles are thermally stable and well soluble in most common solvents, such as tetrahydrofuran, dichloromethane, N, N-dimethyl formamide, dimethyl sulfoxide. Moreover, the photo-and thermo-initiated as well as spontaneous thiol-yne click polymerizations could be used to facilely prepare sulfur-containing hyperbranched polymers. The thiol-yne addition process could be fine-tuned by the control of the polymerization condition, and hyperbranched polymers with diverse topological structures could be provided. The properties and applications including aggregation-induced emission, sensitive explosive detection, self-healing, high refractive index and fluorescent patterning etc, of resultant hyperbranched polymers were also briefly reviewed. In addition, the promising opportunities and directions in this area were also discussed.关键词：Hyperbranched polymers;Click polymerizations;Regioselectivity;Functionalization
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发布时间：2021-05-18 - 摘要：Stimuli-responsive hyperbranched polymers have attracted increasing attention due to their great advantages in biomedical applications. This review highlights their synthesis and self-assembly as well as their biomedical applications. The first part of this review focuses on the synthesis of acid-responsive, temperature-responsive, redox-responsive and photo-responsive branched polymers. These responsive branched polymers are synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization or Michael addition polymerization. The second part of this review focuses on the preparation of nanogels/microgels, nanocapsules and cross-linked large compound vesicles (LCVs) via temperature-induced self-assembly and self-crosslinking of temperature-responsive branched polymers. These polymers aggregate and self-assemble into nanoparticles or vesicles above their lower critical solution temperature (LCST), the formed nanoparticles or vesicles self-crosslink into nanogels/microgels, nanocapsules or cross-linked LCVsvia intermolecular disulfide exchange reaction. The nanogels/microgels are prepared in aqueous solution, and their sizes can be tuned by adjusting the polymer concentration. The nanocapsules and cross-linked LCVs are prepared in emulsion droplets, and their sizes can be tuned by changing the amount of emulsifier. These biocompatible and bioreducible assembled nanostructures have demonstrated great potential to be used as proteins and DNA delivery vectors. The third part of this paper focuses on the applications of the responsive branched polymers in drug and gene delivery. In drug delivery, the hollow voids in the branched polymers architecture can be used to load drugs. However, this loading strategy easily results in leakage of drugs. Based on the abundant functional groups on the branched polymers, drugs can be linked onto the polymers via a labile linkage which can be cleaved under environmental stimuli. In gene delivery, positively charged branched polymer can condense DNA better than their linear counterparts, forming more stable polyplex, and the stimuli-responsiveness of the branched polymers can facilitate the release of loaded DNA.关键词：Responsive;Branched polymers;Self-assembly;Drug delivery;Gene delivery
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发布时间：2021-05-18
Feature Articles
- 摘要：Hyperbranched polymers (HBPs), comprising of dendritic units, linear units and terminal units, are highly branched macromolecules with three-dimensional dendritic globular architecture. Compared with linear polymers, HBPs have shown the characteristics of a large population of terminal functional groups, low or no chain entanglement, small hydrodynamic diameter, low solution or melt viscosity and good solubility. Due to these characteristics, HBPs have attracted global interest from science to industry. In this paper, we review some progress in the synthesis, self-assembly and application of HBPs. The paper includes three parts. In the first part, a short history on the development of HBPs focusing on the introduction of "couple-monomer methodology (CMM)" to prepare HBPs was discussed. A typical example of CMM named as "AA'+B'B2" method was described. In addition, the synthesis of a hyperbranched oxetanemethanol through ring-opening polymerization was also presented. In the second part, the self-assembly of amphiphilic HBPs was summarized according to the morphology of the self-assemblies from the spherical micelles, the vesicles, the sheets or films, the fibers or tubes, to complex supramolecular structures. The mechanism for the self-assembly of the micelles from HBPs was discussed in details. HBPs form unimolecular micelles (UMs) around 10 nm below the critical micellar concentration (CMC). Above the CMC, there are two possibilities for the formation of micelles:one is that HBPs undergo microphase separation and then form micelles with the diameter of the length of two HBPs (around 20 nm or larger), which is named as "microphase-separated small micelles" (ms-SMs) and similar to the star micelles of linear block copolymers in structure; the other is that HBPs form multimolecular micelles (>50 nm) through a mechanism of "multimicelle aggregate" (MMA). The MMA mechanism can also be divided into two mechanisms of "unimolecular micelle aggregate" (UMA) and "small micelle aggregate" (SMA). The MAA mechanism is general and can also be used to explain the large multimolecular micelles self-assembled from other polymers or even small molecules. In the third part of this review, we introduced the applications of HBP self-assemblies in drug delivery, cytomimetic chemistry and monodisperse nanoparticle preparation. The HBP vesicles (named as branched-polymersomes) have displayed good properties like the simple preparation, good membrane fluidity and stability, and the facilely tuned and micrometer-scaled size, which make them the ideal model systems to mimic cell behaviors like fusion, fission, aggregation and so on. All these cytomimetic behaviors can be observed in real time under an optical microscope since the branched-polymersomes have a cell-like size.关键词：Hyperbranched polymers;Self-assembly;Drug delivery;Micelles;Vesicles
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发布时间：2021-05-18 - 摘要：There are diverse photonic structures formed in nature, which can perfectly match the functional and survival demands of the plants or creatures. Inspired by these hierarchical structures, researches have been trying to biomimetic fabrication of responsive photonic crystals through the combination of responsive materials and natural structures for the potential applications in biomedical detections, sensors, decorations and anti-counterfeiting, etc. In this review, progress in stimuli-responsive photonic crystals with biological structures is summarized based on the recent research works, especially those on the variety of the natural photonic crystals with hierarchical structures and the coloration mechanism. The concept of photonic structures in nature is first given and the types are clarified separately with a typical example presented. Generally, these photonic structures can be divided into three categories:1D, 2D and 3D. Accordingly, the coloration mechanism of these structures is explained. With periodic structures arranged in different directions, some of the nature species obtained the magnificent structural colours, which are ultra-difficult for artificial manufacture. Based on these hierarchically photonic structures, functionalization is achieved by introduction of functional materials into the system, such as noble metal, Fe3O4, carbon nanotubes, and organic materials. This review emphasizes on the fabrication, application and responsive mechanism of the responsive photonic crystals based on the responsive polymers. It is known that there are many kinds of stimuli-responsive polymers. By depositing different kinds of stimuli-responsive polymers onto the nature species, that is biotemplates, the stimuli-responsive photonic crystals can be synthesized. The properties of the deposited polymers can be tuned accurately, which could lead to the change of the parameters of the biotemplates including periodic lengths and refractive indexes upon the environmental stimuli signals. Correspondingly, the coloration of the obtained materials is changed. A summary of the existing problems of the photonic crystals with natural structures is also given, making an outlook for the future research work.关键词：Photonic crystals;Stimuli-responsive polymers;Biological structures
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发布时间：2021-05-18 - 摘要：Hyperbranched polymers (HBPs) are highly branched macromolecules with a three-dimensional dendritic architecture. They have four important characteristics:(1) their three-dimensional dendritic architecture can prevent entanglement among polymer chains, thereby resulting in completely different properties from linear polymers; (2) their adequate spatial cavities are beneficial to encapsulate guest molecules; (3) their good solubility and low viscosity can improve processability in comparison with linear polymers; (4) there is a large population of terminal functional groups in HBPs that are easy to for chemical modification. Due to these unique topological structures and distinct physical/chemical properties, HBPs and their assemblies have exhibited great potential in various biomedical areas including drug/contrast agent delivery, gene transfection, protein purification/detection/delivery, antibacterial materials and tissue engineering. The advances of HBPs in biomedical applications have led to an accelerated discovery of HBPs with biodegradable backbones. In recent years, the biodegradable HBPs with excellent biocompatibility, defined structure, and controlled degradation profiles have become increasingly important in therapeutic applications owing to their low toxicity, non-immunogenicity as well as general ease of degradation and metabolization. Up to now, a large number of biodegradable HBPs have been well designed and widely used in therapeutic applications, such as hyperbranched polyester, hyperbranched polyphosphate, hyperbranched polysaccharide, and hyperbranched polypeptide. On the other hand, in order to further study the biodegradable HBPs, a detailed summary and comprehensive understanding on the biodegradable mechanisms of HBPs might be helpful. Considering the differences of degradation reactions, we grouped the biodegradable mechanisms into three types:hydrolysis, enzymolysis and stimuli-responsive degradation. To date, although many elegant reviews on HBPs have been published, a systematic review on the biodegradable HBPs focused on the degradation mechanisms has not been reported so far. Herein, the recent advances of biodegradable HBPs are highlighted. In particular, the biodegradable mechanisms of HBPs, including hydrolysis, enzymolysis and stimuli-responsive degradation, are emphasized. Finally, the applications in disease treatment and possible future directions in this emerging area are also briefly discussed.关键词：Biodegradation;Biodegradable mechanism;Hyperbranched polymer;Disease treatment
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发布时间：2021-05-18
Reviews
- 摘要：Branched CO2-based oligo (carbonate-ether) hexols were synthesized in high productivity and selectivity by immortal copolymerization of CO2 and propylene oxide (PO) in the presence of hydrophobic dipentaerythritol (DPE) using the zinc-cobalt double metal cyanide (Zn-Co-DMC) catalyst. The structure of the CO2-based hexols was confirmed via FTIR, 1H-NMR, 13C-NMR, DEPT-NMR, MALDI-TOF-MS, GPC and DSC. However, because of the overlap of the proton signals assigned to DPE and CO2-based hexols, respectively, it was hard to make sure the fully conversion of the 6 hydroxyl groups in DPE. By using 13C-NMR technique wisely, we confirmed that all the 6 hydroxyl groups participated in the copolymerization due to the chemical shift of characteristic carbon signal of DPE. Moreover, the MALDI-TOF-MS spectrum of the polymer gave a direct visualization of the structure of CO2-based hexols, which contained 6 hydroxyl groups per macromolecule. The number average molecular weight (Mn) of the CO2-based hexol was in good linear relationship to the molar ratio of PO to DPE (PO/DPE), and hence could be precisely controlled from 1500 to 8000. Besides, the rapid chain transfer reaction in the immortal copolymerization afforded the CO2-based hexol with a narrow polydispersity index (PDI) of 1.08 at Mn of 1600, which was reported as one of the narrowest PDI in heterogeneous catalytic systems. Notably, decreasing reaction temperature could substantially improve the catalytic selectivity, e.g., at copolymerization temperature of 50℃, the carbonate unit (CU) content in the CO2-based hexols could reach as high as 60%, while the weight fraction of the unwanted byproduct propylene carbonate (ωPC) could be controlled to as low as 5.5 wt%, although the catalytic productivity declined to 0.14 kg g-1. Unfortunately, the natural hydrophilic polyhydric alcohols, like sucrose and lactose, resulted in uncontrolled reactions and the corresponding CO2-based polyols could not be obtained. These results suggested that the natural polyhydric alcohols could not coordinate to the active center of catalyst.关键词：Carbon dioxide;Propylene oxide;CO2-based hexols;Branched structure
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发布时间：2021-05-18 - 摘要：A series of novel amphiphilic block copolypepides bearing the hydrophilic second-generation (G2) dendritic ether grafts denoted as PBLG-b-(PELG-g-G2) were designed and synthesized by a combination of ring-opening polymerization and click chemistry. First, azido-terminated poly (γ-benzyl-L-glutamate) s (PBLG) with different molecular weights were synthesized by ring-opening polymerization of γ-benzyl-L-glutamate-Ncarboxyanhydride (BLG-NCA) in DMF at room temperature using 3-azido-1-propanamine as initiator and alkyne-terminated poly (γ-2-chloroethyl-L-glutamate) (PCELG) was synthesized by ring-opening polymerization of γ-2-chloroethyl-L-glutamate-N-carboxyanhydride in DMF at room temperature using propargylamine as initiator. The block copolypeptides poly (γ-benzyl-L-glutamate)-block-poly (γ-2-chloroethyl-L-glutamate) (PBLGb-PCELG) bearing chloride side groups were synthesized by click chemistry with high efficiency from the azido-terminated PBLG and the alkyne-terminated PCELG in the presence of CuBr and 1, 1, 4, 7, 7-pentamethyldiethylenetriamine (PMDETA) catalyst system. Then, PBLG-b-PCELG containing chloride side groups was subsequently reacted with excessive sodium azide in DMF to yield a block copolypeptide bearing azido side groups denoted as PBLG-b-(PNELG). The hydrophilic second-generation (G2) dendritic ethers were finally grafted to the side chains of the block copolypeptides PBLG-b-(PNELG) by click chemistry in the presence of CuBr/PMDETA catalyst system and the amphiphilic dendronized block copolypepides PBLG-b-(PELG-g-G2) were successfully synthesized. Their molecular structures were further characterized by 1H-NMR, FTIR and GPC. The thermo-responsive behaviour of PBLG-b-(PELG-g-G2) in water were investigated using UV-Vis and the results showed that the values of the cloud point temperatures (Tcp) of PBLG-b-(PELG-g-G2) became lower with the length increase of the hydrophobic PBLG chain segment. This was explained by the fact that the amphiphilic block copolypeptides PBLG-b-(PELG-g-G2) in water self-assembled into core-shell micelles with the hydrophobic PBLG as the core and the hydrophilic dendronized polypeptide segment as the shell. The degree of hysteresis, defined as the difference in the cloud points upon heating and cooling, in each system lowered with the decrease in amphiphilic block copolypepide concentrations for micelles. The synthesized PBLG-b-(PELG-g-G2) may be expected to have good application prospects in the biomedical field due to the excellent biocompatibility of their structural units.关键词：Block copolymer;Polypeptide;Ring-opening polymerization;Click chemistry
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发布时间：2021-05-18 - 摘要：Water content is one of crucial factors affecting the morphology of polymer aggregates in solution. In the present work, we synthesized an amphiphilic hyperbranched copolymer (DNS-PEHO-star-PEO) with a hydrophobic poly[3-ethyl-3-(hydroxymethyl) oxetane] (PEHO) core and hydrophilic poly (ethylene oxide) (PEO) arms, in which the PEHO core was labelled with dansyl (DNS) fluorophore. The degree of branching (DB) of the hyperbranched polymer was around 0.4 and the molar fraction of the PEO arms wasca. 0.7. Through a fluorescence labeling approach coupled with transmission electron microscopy (TEM), dynamic light scattering (DLS) and photoluminescence (PL) spectrometry analyses, etc., we studied the effect of water content on the morphology of the hyperbranched polymer aggregates in solution. Interestingly, it was found that in tetrahydrofuran (THF)/H2O mixed solvents with < 20 vol% water content, DNS-PEHO-star-PEO self-assembled into spherical micelles with diameters of < 20 nm, which possessed a DNS labeled PEHO core and a PEO corona; when the water content increased to ca. 75 vol%, the hyperbranched copolymers organized into "multi-micelle aggregates (MMAs)" with diameters in the range of 300-400 nm, which consisted of a large amount of small spherical micelles; while in pure water, the hyperbranched copolymers aggregated into micrometer-sized giant vesicles, which emitted green photoluminescence upon excitation under fluorescence microscope. The DNS-PEHO-star-PEO aggregates of different morphologies show different PL emission spectra in THF/H2O solutions, owing to the variation of the molecular conformation of the DNS fluorophore in the hyperbranched polymer assemblies of various morphologies. Such a unique PL feature allows the plotting of a morphological phase diagram by water content as a function of the wavelength at the PL emission maximum. The phase diagram clearly shows the effect of water content on the morphology of the PEHO-star-PEO aggregates in THF/H2O solutions. The fluorescence labeling approach is expected to be a powerful tool in monitoring the morphological transition of polymer aggregates in solution.关键词：Hyperbranched copolymers;Self-assembly;Fluorescence labeling;Water content;Morphological transition
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发布时间：2021-05-18 - 摘要：We developed a synthetic method for amphiphilic and highly branched block copolymers composed of polystyrene and poly (N-isopropylacrylamide) (PNIPAM) through copolymerization of an anionic inimer (synthesized from monoaddition of 1, 3-bis (1-phenylvinyl) benzene (MDDPE) with s-butyllithium) and styrene, followed by mechanism transformation from living anionic to controlled radical polymerization based on reversible addition-fragmentation chain transfer process. The mechanism transformation was achieved on the basis of conversion of living anionic species into thiocarbonylthio moieties by sequential reaction with CS2 and 1-phenylethyl bromide, affording a dendritic chain transfer agent (Dendritic-CTA). The resulting Dendritic-CTA was further employed to mediate RAFT polymerization of NIPAM to give amphiphilic and highly branched block copolymer. A series of amphiphilic and highly branched block copolymers were thus prepared by changing the feed ratio of NIPAM to Dendritic-CTA. The successful formation of Dendritic-CTA was confirmed by ultraviolet spectrum (UV), the structures of the Dendritic-CTA and the highly branched amphiphilic block copolymers were further characterized by 1H nuclear magnetic resonance (1H-NMR), gel permeation chromatography (GPC) equipped with multiangle laser light scattering detector. The solution properties of the highly branched amphiphilic block copolymers were investigated by fluorescence emission spectra (using nile red as the fluorescent probe), dynamic light scattering (DLS), and transmission electron microscopy (TEM). The fluorescence results show that the amphiphilic highly branched polymers have a low critical aggregation concentration (CAC) around 0.0035 mg/mL, and a temperature dependent multistage aggregation of the products in water was observed in the test of DLS. The DLS results also showed that the amphiphilic and highly branched block copolymers could form micelles withRh size of 135 nm in water; the TEM results further illustrated that the amphiphilic and highly branched products could form spherical micelles and the diameters of the micelles were around 40 nm. Furthermore, the ability of the amphiphilic and highly branched products to stabilize the emulsion was studied using different oil/water systems. The results indicated a strong ability of emulsification arising from highly branched topology. Reversible formation of W/O and O/W was also observed due to the presence of PNIPAM segment with lower critical solution temperature (LCST). In addition, the emulsifying properties of the amphiphilic and highly branched products were closely dependent on the polarity of the solvents which were use to dissolved the polymers initially. The process may serve as a versatile approach to make amphiphilic and highly branched block copolymers with temperature responsiveness.关键词：Highly branched polymer;Living polymerization;Mechanism transformation;Inimer;Amphiphilicity
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发布时间：2021-05-18 - 摘要：Poly (ethylene glyco1)-g-poly (γ-benzyl-L-glutamate) (PEG-g-PBLG) graft copolymers, bearing hydrophilic PEG backbone and hydrophobic PBLG side chain, were synthesized via ring opening polymerization of γ-benzyl-L-glutamate-N-carboxyanhydride (BLG-NCA) using PEG-g-NH2 as the initiator. The molecular weight and polydispersity index of the graft copolymers as well as conformation of PBLG chains were characterized by proton nuclear magnetic resonance (1H-NMR), gel permeation chromatography (GPC), and Fourier transform infrared spectrum (FTIR), respectively. Self-assemblies were prepared by a selective solvent method with tetrahydrofuran (THF) as the initial common solvent and water as the selective solvent. The critical water content (CWC) for the graft copolymer aggregation was determined by turbidity measurement (OD). The CWC value decreases from 17.3 wt% to 12.8 wt% gradually with the increase in PBLG length (the initial concentration is 0.5 g L-1). The morphologies and structures of the formed aggregates were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atom force microscopy (AFM), and laser light scattering measurements (LLS). The results show that the graft copolymers are able to self-assemble into spherical compound micelles when the PBLG side chain is relatively short. As the PBLG length increases, the aggregates gradually transform to rod-like aggregates and vesicles. In addition to the experiments, the self-assembly of the graft copolymers was investigated using dissipative particle dynamics (DPD) simulation based on a coarse-grained coil-g-rod graft copolymer model. The simulation results were in agreement with the experimental findings, and additional information such as chain distribution of copolymers in aggregates was obtained. Besides, it was found that the initial polymer concentration affected the aggregate size but no significant influence was observed on the aggregate morphology. When prepared at higher initial polymer concentration (1.0 g L-1), the aggregates obtained were much larger in size and narrower in size distribution. Finally, based on both the experimental and the simulation results, a mechanism for the self-assembly of PEG-g-PBLG graft copolymers was proposed.关键词：Graft copolymer;Polypeptide;Rigid chain;Vesicle;Dissipative particle dynamics simulation
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发布时间：2021-05-18 - 摘要：A novel synthetic strategy of β-cyclodextrin (β-CD) polyrotaxane (PR) was developed using poly (propylene glycol) (PPG) terminated by 3, 4, 5-tris (prop-2-yn-1-yloxy)-benzamide groups as the axle and 2-azidoethanol as the end-capping reagent. Being different from the traditional synthetic strategy of CD PR, where bulky end-capping reagents were generally used, this strategy used small-sized 2-azidoethanol as the end-capping reagent to produce 3 triazole rings at each end by Cu (I)-catalyzed alkyne-azide 1, 3-dipolar cycloaddition (CuAAC). The triazole rings thus produced blocked the CD rings on the PPG axle. The small size of the end-capping reagent could effectively reduce the steric hindrance of the end-capping reaction. Furthermore, the end-capping reaction CuAAC was conducted in water, preventing the polypseudorotaxane (PPR) from dissociation that generally occurred in organic solvents due to the absence of hydrophobic interaction. The synthesized β-CD PR was characterized structurally by 1H-NMR and 2D rotating-frame Overhauser effect spectroscopy (2D ROESY). 1H-NMR spectrum of the synthesized β-CD PR showed broad and unresolved proton signals, revealing that the supramolecular architecture of the β-CD PR was stable in DMSO and the rotaxanation significantly reduced the conformational flexibility of β-CD and PPG axle, causing the broadened signals. On the basis of the integral intensity of the 1H-NMR signals, it was calculated that about 3 β-CD rings were locked on one PPG axle. In the 2D ROESY spectrum of β-CD PR, a strong cross-peak appeared, owing to the nonbonding interaction between the methyl protons (δ=1.08) of the PPG axle and the C (3) H (δ=3.59) and C (5) H (δ=3.47) protons of the β-CD units, confirming that the CD rings were really threaded onto the PPG axle and successfully locked by the end-capping groups. Using the abundant hydroxyl groups in PR, we performed the PEGylation and fluorescence labeling of theβ-CD PR and studied the cytotoxicity and cellular uptake of the modified PR, the results indicated that the modified β-CD PR had no detectable cytotoxicity and could be internalized by cells through an endocytosis process.关键词：β-Cyclodextrin polyrotaxane;Synthetic strategy;Cytotoxicity;Cellular uptake
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发布时间：2021-05-18 - 摘要：With cotton fabrics as substrates, γ-ray irradiation was used to initiate the graft polymerization of lauryl methacrylate (LMA), to attach polystyrene (PS) nanospheres to the cotton fabrics in by covalent bonding via the grafted chains, form a nano-scale coarse structure with low surface energy on the surface of cotton fabrics, and obtain dynamic superhydrophobic cotton fabrics with a low water droplet sliding angle. The grafting kinetics was studied and the degree of grafting (DG) increased regularly with the increasing of the concentration of the monomer. Therefore the DG could be controlled by changing the conditions of the graft polymerization. Fourier transform infrared spectroscopy (FTIR) analyses were carried out on the cotton fabrics after the graft and the results confirmed the presence of PS nanospheres and grafted PLMA chains on the modified cotton fabrics. Scanning electron microscopy (SEM) analysis showed that the attachment of the PS nanospheres onto the cotton fabrics led to the formation of a nanoscale coarse structure on the surface of the cotton fibers. The contact angle of water droplet on the modified cotton fabric was higher than 150°, which demonstrated that the modified cotton fabrics were superhydrophobic. Relative to the cotton fabrics solely grafted with LMA, the PS nanospheres-decorated cotton fabrics had a significantly reduced water droplet sliding angle, and possessed dynamic superhydrophobicity. This should be attributed to the "lotus effect" of the surface of the modified cotton fabrics containing low surface energy and regular nano-scale roughness structure formed by the attachment of PS nanospheres. The softness of the cotton fabrics was characterized through the measurements of their flexural rigidity before and after their modification. The results showed that radiation-induced graft polymerization of LMA and the immobilization of PS nanospheres did not influence the wearability of the cotton fabrics, as it did not have a significant effect on their softness.关键词：Dynamic superhydrophobic;Radiation-induced graft polymerization;Cotton fabrics;Sliding angle
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发布时间：2021-05-18 - 摘要：To search safe and evaluate non-viral nucleic acids carrier, a series of polyphenylalanine and phenylalanine grafted low molecular weight PEI with a molecular weight of 1.8×103 (PEI1.8k-g-PPhe and PEI1.8k-g-Phe) were prepared by NCA ring opening polymerization initiated by PEI-1.8k and phenylalanines conjugation to PEI-1.8k, respectively. The polymers and the complexes of PEI1.8k-g-PPhe/DNA and PEI1.8k-g-Phe/DNA were characterized by nuclear magnetic resonance (NMR) analysis, particle size analysis, zeta potential analysis, luciferase analysis, flow cytometry (FCM) analysis and confocal laser scan microscopy (CLSM). In order to compare the property for compacting DNA into nanoparticles, the particle size and zeta potential analysis were carried out. Both PEI1.8k-g-PPhe and PEI1.8k-g-Phe showed suitable particle size and zeta potential for gene delivery. The particle size of PEI1.8k-g-PPhe10/DNA complexes were about 150 nm and the zeta potentials were about +16 mV, which were suitable for the in vitro experiments. Moreover, cell viability, after treating with different copolymers at various concentrations, was studied by an MTT assay. The reduced cytotoxicity of PEI1.8k-g-PPhe and PEI1.8k-g-Phe may be because of the introduction of neutral hydrophobic phenylalanine moieties. And both of the PEI1.8k-g-PPhe and PEI1.8k-g-Phe had lower cytotoxicity (above 70% viability at a higher concentration 1 mg/mL) than that of PEI with a molecular weight of 2.5×104 (PEI-25k) in HeLa cells. The in vitro gene transfection of PEI1.8k-g-PPhe10 and PEI1.8k-g-Phe10 was conducted in human cervical cancer (HeLa) and breast cancer (MCF-7) cells. In both of the cells, PEI1.8k-g-PPhe10 exhibited much higher gene transfection efficiency. PEI1.8k-g-PPhe10/DNA complexes showed remarkable gene transfection efficiency, which was about twelve times higher than that of PEI-25k. The endocytosis efficiency of PEI1.8k-g-PPhe10/DNA and PEI1.8k-g-Phe10/DNA were quantified using flow cytometry. Due to their regular polymer chain, PEI1.8k-g-PPhe10/Cy5-DNA showed better internalization efficiency than PEI1.8k-g-Phe10/Cy5-DNA, PEI-25k/Cy5-DNA and PEI-1.8k/Cy5-DNA. The CLSM assay was carried out to verify the internalization efficiency together which also indicated that PEI1.8k-g-PPhe10/Cy5-DNA induced higher intracellular uptake efficiency than the others.关键词：Polyphenylalanine;Low molecular weight PEI;Gene carriers;Gene transfection
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发布时间：2021-05-18 - 摘要：Imine 1 with a phenylene and a tetrafluorophenylene units tethered by an imine bond was synthesized, and its self-assembly and thermotropic liquid crystalline behaviour were studied. Imine 1 showed a high thermal stability with only 5% mass loss occurred at 346℃ as revealed by thermal gravimetric analysis (TGA). The heating process of differential scanning calorimetry (DSC) analysis revealed two endothermic peaks at 93 and 118℃, which were attributed to the transition from the crystalline phase into the liquid crystalline phase and the transition from liquid crystalline phase into the isotropic phase, respectively. Meanwhile, similar phase transition behaviors were observed in the cooling process, with phase transition temperatures at 97 and 84℃, respectively. In addition, in the polarized optical microscopy (POM) analysis, imine1 melt and turned birefringent at 110℃, then it transformed into an isotropic liquid at 118℃. Upon slowly cooling at a rate of 1 K/min, an occurrence of a liquid crystal birefringence was detected again at 106℃. Thus, the results obtained with POM agreed well with DSC thermograms, both characterizations indicated imine 1 formed liquid crystalline phase from 93℃ to 118℃. Wide-angle X-ray diffraction (WAXD) revealed an oblique columnar lattice of imine 1 in the liquid crystal state, with a=4.90 nm, b=3.51 nm and γ=110°. Two-dimensional X-ray diffraction (2D XRD) patterns of oriented sample of imine 1 further confirmed its oblique columnar liquid crystalline phase. The results revealed that arene-perfluoroarene face-to-face stacking and amide-amide hydrogen bonding interactions were responsible for the formation of columnar aggregation of imine 1. Furthermore, disordered dodecyloxyl chains on both ends of the molecule were proposed to interpenetrate with one another, which formed microphase separation in the aggregation, and contributed to the formation of long-range ordered columnar liquid crystalline phase.关键词：Dendrimer;Arene-perfluoroarene interaction;Hydrogen bonding;Liquid crystal
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发布时间：2021-05-18 - 摘要：Compatibilization of immiscible polymer blends using reactive nanoparticles as the compatibilizer is reported. The reactive hybrid nanoparticles, POSS (epoxy)4-g-PMMA4, were synthesized via eight epoxy based octa polyhedral oligomeric-silsesquioxane (POSS (epoxy)8) initiated ring-opening grafting of a carboxyl acid-terminated polymethylmethacrylate (PMMA-COOH) (Mn, side chain=3850). The molecular structure of the synthesized POSS (epoxy)4-g-PMMA4 was investigated by Fourier transform infrared spectroscopy (FTIR) spectra, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and nuclear magnetic resonance (1H-NMR). Both FTIR and NMR results indicated that PMMA oligomers were chemically grafted onto the POSS and four epoxide groups remained on the POSS core. DSC measurement showed that the glass transition temperature (Tg) of the grafted PMMA was lower than that of the PMMA oligomer before grafting. POSS (epoxy)4-g-PMMA4 was then used as the reactive compatibilizer for the immiscible polyvinylidene fluoride/poly (L-lactide) (PVDF/PLLA) blends. The reactive epoxide groups of POSS (epoxy)4-g-PMMA4 reacted with the end COOH groups of PLLA, and the PMMA tails on the POSS (epoxy)4-g-PMMA4 had specific interactions with PVDF molecular chains. It was found that the domain size decreased drastically for the compatibilized blends and the interface adhesion was improved. The Tg of both PVDF and PLLA shifted to each other after the incorporation of the reactive nanoparticles. At the same time, the phase size decreased continuously with increasing the loading of the reactive hybrid nanoparticles. It is therefore considered that the reactive nanoparticles formed a Janus structure located at the interface and took the role as the effective compatabilizer for PVDF and PLLA after reactive blending. Moreover, the compatibilized blends exhibited drastic improvements in the mechanical properties, compared with the uncompatibilized blends. The tensile strength and elongation at break were 50 MPa and 7.8%, respectively, for the blend with 5 wt% POSS (epoxy)4-g-PMMA4, while those for the uncompatibilized blend were 40 MPa and 3%. This research provides a new possibility to compatibilize immiscible polymer blends by inorganic nanoparticles.关键词：Grafting;In situ compatibilization;Reactive blending;Immiscible
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发布时间：2021-05-18 - 摘要：Hyperbranched polyurethane (HBPU), with highly branched three-dimensional topological structures and outstanding mechanical properties, have recently received increasing attention in the modification of epoxy resins. Herein, HBPUs with different composition were synthesized and added into epoxy resins. Homogenous blending system and heterogeneous blending system were obtained by incorporating different HBPUs. The effect of micro-phase separation on toughening epoxy resins was removed by the homogeneous system, which proves the HBPU modifying epoxy resins. Aromatic hyperbranched polyurethane (M-HBPU) and aliphatic hyperbranched polyurethane (H-HBPU) were prepared through the reaction of diethanolamine with aromatic diisocyanate (MDI) and aliphatic diisocyanate (HDI) respectively, and the obtained polymers were added into epoxy resin as modifiers to make samples for test. The structures of the M-HBPU and H-HBPU were confirmed by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR). The micro-phase structures were studied by scanning electronic microscopy (SEM) and the images showed that the blending of M-HBPU and epoxy resin was homogeneous after curing, while the blending of H-HBPU and epoxy resin was phase-separated. The mechanical properties, including flexural strength, impact strength, tensile strength and storage modulus, of the modified epoxy resins were improved after the treatment with both M-HBPU and H-HBPU. There was an optimal amount of the hyperbranched polyurethanes in the modified epoxy resin system. Meanwhile, differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) results revealed that the thermal performance of epoxy resins per-treated with the M-HBPU was enhanced markedly, as compared with the pure epoxy resins. The homogeneous phase system of epoxy resins was obtained successfully after the modification with M-HBPU. All these results indicated that the mechanical properties and thermal performances of the modified epoxy resin could be improved directly by M-HBPU without the effect of micro-phase separation.关键词：Hyperbranched polyurethane;Epoxy resin;Modify;Micro-phase structurey
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发布时间：2021-05-18 - 摘要：Long-range and one-dimensional nanofibers assembled by hyper branched molecules were observed in experiments. Intuitively, the isotropic hyper branched molecules are not expected to form regularly one-dimensional self-assembly structures. The formation mechanism and detailed structures of the self-assembly nanofibers are still unclear. In this work, we employed molecular dynamics simulation to study the formation process of these one-dimensional nanofibers. We built the coarse-grained model of the hyper branched molecules reported in experiments, and studied the formation of Langmuir condensed monolayer by gradually decreasing the surface area of air-water interface, where the hyper branched molecules were adsorbed. The detailed structures of the self-assembled nanofibers were identified in simulation, which can help to understand experimental results from a microscopic point of view. To be specific, we observed the one-dimensional nanofibers which consist of only one row of molecules, different from the speculation in experiments that the nanofibers may consist of multi-rows of molecules. We also found that the hydrophobic alkyl tails were oriented upwards to the air, covering most part of the core region of the hyper branched molecules, in agreement with the experiments. The influence of the interactions between terminal branches on the self-assembled structures was also studied. With strong attractions between terminal branches, large sheets of aggregation structure were formed by the hyper branched molecules. While with weak attractions, short linear micelles were formed. The one-dimensional nanofibers were formed only when the attractions between terminal branches were in a range of moderate intensity. In addition, we studied also the influence of the interactions between terminal branches and water on the formation of the nanofiber structure. It was found that suitable hydrophobicity was crucial for the formation of the nanofiber structure, and the hydrophilic terminal branches hindered the formation of the one-dimensional nanofibers. Instead, short linear micelles will be formed between the hyper branched molecules and the hydrophilic terminal branches.关键词：Hyper branched molecules;Nanofibers;Molecular dynamics simulation
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发布时间：2021-05-18 - 摘要：Dendrimers characterized by monodisperse hyperbranched structure have been applied in many fields due to their unique properties such as precise structure, plenty of internal cavities and high density of surface functional groups. Dendrimers with internal and peripheral dual-functional groups attract much attention because of their versatility in functionalization. Herein, started from allylamine, followed by BOC protection and m-CPBA oxidation, we synthesized 3-BOC-protected amino-1, 2-propylene oxide (BN-PO). Using BN-PO as the only monomer and by sequential amine-epoxy click reaction and BOC-deprotection, a new type of poly (hydroxypropylene imine) (HOPPI) dendrimer, with internal hydroxyl groups and peripheral amine groups, was synthesized. In the epoxy-amine click reaction, a slight excess of monomer (1.2 equiv.) was used to drive the reaction to completion, DIPEA or DABCO was used as catalyst to accelerate the reaction. A simple precipitation in hexane was sufficient to remove the unreacted monomer. HCl was used for BOC-deprotection. The resulting hydrochloride was subsequently removed using Ca (OH)2 to expose free amine groups. The fourth generation dendrimer, containing 60 internal hydroxyl groups and 32 peripheral amine groups, was easily obtained using this simple and efficient synthesis procedure. The dendrimer structures were confirmed by1H-NMR spectra, mass spectra and gel permeation chromatography. The corresponding peak integral ratios in 1H-NMR spectra showed proper structure of dendrimers. A side reaction in the epoxy-amine click reaction, due to the attack on different carbon, was also revealed. Mass spectra showed the mass-to-charge ratio of dendrimers, which further confirmed the precise structure of dendrimers. Gel permeation chromatography (GPC) showed a narrow distribution of the molecular weight of the dendrimers. The molecular weight obtained from GPC was smaller than the theoretical value as the hydrodynamic volume of the dendrimer was smaller than that of the linear polymers of the same molecular weight. Thus, this article provides a simple and convenient approach to synthesize monodisperse HOPPI dendrimers with high density of dual-functional groups, which are easy for various modifications in order to adopt for different applications.关键词：Dendrimer, Facile synthesis;Epoxide-amine reactions;Click reaction;Internal and peripheral dual-function groups
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发布时间：2021-05-18 - 摘要：A series of star dendronized polymers PPDSn-b-PG1m-SS, constituted by cross-linked disulfide core and oligoethylene glycol (OEG)-based dendronized polymer arms, were designed and synthesized by the "arm first" approach for the first time. Due to the large difference between molar masses of dendronized macromonomer and conventional monomers, diblock copolymers used for core crosslinking were prepared by using the monomer bearing pyridyldisulfide side groups to form the first block. Therefore, the macro chain transfer agents (PPDS) were obtained by reversible addition-fragmentation chain transfer (RAFT) polymerization of monomer bearing pyridyldisulfide side groups. These terminally reactive macro chain transfer agents were subsequently used to further initiate polymerization of OEG-based dendritic monomer (MG1), affording well-defined diblock copolymers. Finally, the objective star dendronized polymers were prepared based on thiol-disulfide exchange reaction by adding 1, 2-ethanedithiol as cross-linkers. The structure and molecular weights of the resulting polymers were characterized by 1H-NMR and GPC. UV-Vis spectroscopy and AFM were used to investigate the thermoresponsive behaviors and morphologies of the polymers, respectively. The results showed that star dendronized polymers were successfully prepared. Similar to their linear dendronized counterparts, these star polymers showed fast and sharp phase transitions with small hysteresis. Ascribed to the dendronized topology, these star dendronized polymers were directly visualized by AFM on mica to have star or spherical morphologies, dependent mainly on the chain length of the dendronized polymer arms. Therefore, we provide here the first example for convenient synthesis of thermoresponsive star dendronized polymers through core cross-linking of diblock dendronized polymers, which provide a platform to investigate the topological effects on stimuli-responsiveness of dendronized polymers. Due to the dynamic characteristics of thiol-disulfide exchange reaction, these star dendronized polymers have the potential to be reversibly transferred into linear counterparts. Overall, combination of the unique architecture and performance characteristics of star polymers with cylindrical morphology of oligoethylene glycol (OEG)-based thick dendronized polymers afforded not only novel star dendronized polymers, but also endowed the objective polymers with characteristic thermoresponsiveness for potential bioapplications.关键词：Thermoresponsiveness;Oligoethylene glycol;Dendronized polymers;Star polymers
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发布时间：2021-05-18 - 摘要：Development of supramolecular dendritic systems becomes a promising strategy on fabrication of efficient nanoplatforms for therapeutic agent delivery. Arginine-rich and lipoic acid-functionalized peptide dendrons were accurately synthesized using divergent approach and characterized with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Critical aggregation concentration of the amphiphilic peptide dendron was determined to be 209.8 μg/mL using pyrene as fluorescence probe. After supramolecular self-assembly of these peptide dendrons into nanoparticles in water, a catalytic amount of dithiothreitol (DTT) could induce polymerization to generate cross-linked and bio-cleavable dendritic systems (BCDSs) for improving the gene delivery efficiency in normal cells and tumor cells. The size of the disulfide cross-linked dendritic systems became much smaller (~72 nm) than the size of the non-crosslinked dendritic assemblies (~107 nm), which agreed well with the transmission electron microscope results. Agarose gel electrophoresis retardation assay indicated BCDSs completely condensed DNA at an A/P ratio of 5. An appropriate complex size of 80 nm was found at A/P of 20 with uniform spherical nanostructure. The BCDSs/DNA complex could efficiently protect DNA against DNase degradation, while reductive condition (10 mmol/L DTT) could induce the disintegration of nanocomplex and the release of DNA. Then, the confocal laser scan microscopy images indicated that intracellular reductive condition triggered cleavage of disulfide-stabilized supramolecular dendritic system and deliveried DNA into nucleus. Owing to the efficient DNA internalization and redox-responsive release of the BCDSs/DNA complexes (A/P=20), green fluorescent protein expression was much better than the positive control of PEI group (N/P=10, in the absence of fetal bovine serum). Quantitative result demonstrated that BCDSs could largely enhance the transfection efficiency of pGL3-Luc by 4.2 times, 2.7 times and 3.4 times in HEK 293, HepG2 and Hela cell lines as compared with positive PEI group. Moreover, BCDSs were obviously nontoxic to all the three cell lines even at a high concentration of 60 μg/mL with more than 90% cell survived. However, PEI exhibited serious toxicity at low concentration of 10 μg/mL. This tailor-made molecular and supramolecular fabrication of biological cleavable dendritic systems holds great potentials in developing smart nanoplatforms for satisfactory gene delivery.关键词：Dendritic assemblies;Arginine-rich corona;Disulfide stabilization;Redox-responsive delivery;Gene transfection
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发布时间：2021-05-18 - 摘要：It is of great importance to polymerize multivinyl monomers and simultaneously circumvent uncontrollable polymerization process and low gel point. Hereby, a type of divinyl monomer:ethylene glycol dimethacrylate (EGDMA) was successfully homopolymerized by kinetically controlled Cu0 and CuⅡ-meadiated reversible-deactivation radical polymerization (RDRP). The kinetic study showed a well-controlled polymerization behaviour. During the initial stage, a linear chain propagation was observed with a low polydispersity ( < 1.35) demonstrating the controlled/living polymerization feature. However, the products obtained during this stage showed a high consumption of pendent vinyl groups (around 28%) based on the analysis by proton nuclear magnetic resonance ( 1H-NMR). This high pendent vinyl conversion in the linear chain propagation stage is attributed to the significant involvement of the intramolecular cyclization. The promotion of the intramolecular cyclization and suppression of the intermolecular crosslinking is achieved by the low kinetic chain length and low polymer volume concentration. Given the coexistence of linear chain propagation and high pendent vinyl conversion, the novel single chain cyclized polymer structure was formed during this process, which was further used as polymeric nanoparticles to modify the viscoelasticity of linear poly (methyl methacrylate) (PMMA) melts. The essentially similar chemical structure between the EGDMA and MMA ensures the minimization of enthalpic interactions and dispersion forces between the nanoparticles and linear melts. The oscillatory rheology study and the subsequent time temperature superposition based on the Williams-Landel-Ferry equation demonstrated the coexistence of the segmental relaxation at high frequencies and chain relaxation at low frequencies. The complex viscosity studied as a function of the shear frequency showed the decrease in terminal viscosity with addition of 10 wt% single chain cyclized polyEGDMA nanoparticles. A further decrease was also observed with the addition of 20 wt% nanoparticles, which is not in agreement with Einstein relationship between the complex viscosity and fraction of added particles. This strategy provides a simple and efficient approach to control polymerization of multivinyl monomers, and the unexpected decrease in viscosity of the blend system should in principle open a new avenue to modify polymer melts and molten systems.关键词：Free radical polymerization;Multivinyl monomers;Polymeric nanoparticles;Viscoelasticty
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发布时间：2021-05-18 - 摘要：Block copolymer micelles of poly (ethylene glycol)-block-poly (L-lysine) (PEG-b-PLys) was used to load fullerene (C60) and zinc tetrakis (4-sulfonatophenyl) porphyrin (ZnTPPS) in water. The diblock copolymer of PEG-b-PLys was firstly synthesized via ring-opening polymerization. Then the PEG-b-PLys/C60 micelles were prepared by association between PEG-b-PLys and C60 in aqueous solution. ZnTPPS was added to the PEG-b-PLys/C60 micelle solution and PEG-b-PLys/C60/ZnTPPS complex micelles were finally obtained by electrostatic interaction between ZnTPPS and PLys. The structure and photochemical properties of the PEG-b-PLys/C60/ZnTPPS complex micelles were characterized by dynamic light scattering, transmission electron microscopy, UV-Visible spectroscopy and fluorescence spectroscopy. The results showed that the PEG-b-PLys/C60/ZnTPPS complex micelles were reasonably monodisperse with an average hydrodynamic diameter of 80 nm. The complex micelles showed the typical UV-Vis spectra of ZnTPPS and C60. The Soret-band peak of ZnTPPS in the complex micelles was red-shifted from 421 to 430 nm, which was possibly caused by electron transfer from the ZnTPPS to the fullerene. In addition, the fluorescence emission spectra of ZnTPPS was obviously quenched in the complex micelles. These results suggested that ZnTPPS was assembled successfully into PEG-b-PLys/C60 micelles. In order to investigate the role of C60 in the photoprotection of ZnTPPS, the illumination of ZnTPPS encapsulated in different micelles was carried out under identical conditions using a 360 nm cut-off filter. Compared with ZnTPPS in the PEG-b-PLys/ZnTPPS electrostatic micelles, the ZnTPPS loaded in the complex micelles possessed higher photostability because of the reduced generation of singlet oxygen. The photoreduction of methyl viologen hydrate (MV2+) was chosen as the model reaction to evaluate the electron-transfer efficiency of the complex micelles. The amount of MV+· produced by the complex micelles was higher than that by both free ZnTPPS and PEG-b-PLys/ZnTPPS electrostatic micelles. Thus the complex micelles showed better electron transfer ability and higher photoactivity because of the electron transfer from the porphyrin to the fullerene in the complex micelles.关键词：Fullerene;Zinc porphyrin;Complex micelles;Photoactivity
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发布时间：2021-05-18
Research Article
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