Hierarchical self-assembly of p-terphenyl derivative with dumbbell-like amphiphilic and rod-coil characteristics

As water is gradually added, a p-terphenyl derivative with dumbbell-like amphiphilic and rod-coil characteristics can hierarchically self-assemble to metastable rectangle columns architecting sheets first and then to stable quasi-hexagonal columns architecting rolled sheets, and finally to rod-like nanostructures in MeOH/H₂O solution. Interestingly, the formed sheet, rolled sheet, and nanorod possess blue-light emitting property.     

Helical structures architecture of l-{2-(4-hydroxy-phenyl)-1-[(pyren-1-ylmethyl)-carbamoxyl]-ethyl}-carbamic acid tert-butyl ester

A new pyrenemethylamine substituted l-Boc-tyrosine derivative was synthesized and characterized. UV-vis, FL, CD, and light scattering experiments proved that the chiral molecules were able to self-assemble for formation of new aggregate structure. The SEM and AFM images indicated that the helical wires could be fabricated by π-π stacking interaction between adjacent pyrene molecules.     

Spectral and self-assembly properties of a series of asymmetrical pyrene derivatives

A series of pyrene derivatives with different asymmetrical substituents were successfully synthesized and characterized. The geometrical electronic structures of the asymmetrical pyrene derivatives were performed by density functional theory （DFT） calculations. The results of photophysical spectra and electrochemical analysis indicated that the optical or electric properties of the pyrene derivatives could be tuned by adjust the π-conjugation lengths of the substituents. Furthermore, through a phase exchange self-assembly method, the highly organized morphologies were observed by SEM.     

Rational construction of self-assembly azobenzene derivative monolayers with photoswitchable surface properties

hoto-responsive azobenzene (ABZ) derivatives with different end groups (R) were employed to construct selfassembled monolayers (SAMs) on silicon substrates. The SAMs based on hydrophilic (4-(4'-aminophenylazo) benzoic acid, ABZ-COOH) show excellent reversible photoswitching performance with a large contact angle change of 35° under optimized process.     

Novel fluorescent amphiphilic block copolymers: Controllable morphologies and size by self-assembly

New fluorescent amphiphilic copolymers polyacrylamide-b-poly(p-methacrylamido)acetophenone thiosemicarbazone (PAM-b-PMATC) were synthesized by atom transfer radical polymerization (ATRP) method. The structures of polymers were confirmed by ¹H NMR and gel permeation chromatography-multi-angle laser light scatting (GPC-MALLS). PAM-b-PMATC showed a broad emission peak about 388 nm excited at 318 nm in aqueous solution. The self-assembly behavior of PAM-b-PMATC in the binary mixture formamide/water was observed by transmission electron microscope (TEM). It indicated that PAM-b-PMATC-I and -II with the same PAM block self-assembled to vesicles and sunflower-like micelles. The water fraction in the mixture could control the size and thickness of vesicles. Vesicle size increased from 50 to 420 nm and vesicle thickness changed from 5 to 50 nm with water content ranging from 33 to 90 vol.%. In addition, the cytotoxicity in vitro of PAM-b-PMATC-I and its nanoparticles loaded with methotrexate (MTX) were evaluated by MTT assay.     

Amino-substituted amphiphilic calixarenes: self-assembly and interactions with DNA

The amphiphilic 5,11,17,23-tetramino-25,26,27,28-tetradodecyloxycalix[4]arene is shown to self-assemble as stable and well-defined Langmuir monolayers at the air-water interface. The effect of the presence of DNA in the subphase reveals interactions taking place at the interface between the positively charged surface and the negatively charged DNA, causing an expansion of the monolayers and a phase transition from a liquid-condensed to a liquid-expanded phase; a slight decrease in the stability of the monolayers is also observed. The title compound is shown to self-assemble, with the absence of a cosurfactant, as stable colloidal suspensions. Photon correlation spectroscopy, zeta-potential measurements, and atomic force microscopy reveal that these colloidal suspensions present a monodisperse size distribution and are composed of positively charged solid lipid nanoparticles (SLNs), with an average hydrodynamic diameter of 190 nm and a surface potential of +13.2 mV. The interaction of these SLNs with double-stranded DNA is demonstrated.     

Supramolecular helix of an amphiphilic pyrene derivative induced by chiral tryptophan through electrostatic interactions

An amphiphilic pyrene derivative (PyDNH3) bearing positively charged ammonium cations has been synthesized and characterized. Self-assembly of PyDNH3 in the presence of chiral tryptophan derivatives was investigated in ethanol/water by optical and chiroptical spectra, indicating the formation of helical aggregates. Scanning electron microscope (SEM) images showed the formation of ring-shape structures.     

Templated self-assembly of wedge-shaped DNA arrays

We demonstrate the use of a one-dimensional template to control the shape of a two-dimensional array self-assembled from a minimal set of DNA tiles. A periodic single-stranded template seeds tile assembly. A unique vertex tile at the 5′ end of the template controls the positioning of edge and body tiles to create a wedge-shaped array. The vertex angle of the array is approximately 12°; edge lengths are of the order of 1 μm.     

An amphiphilic supramolecular polymer: Construction,self-assembly and pH-responsive behavior in water

A novel amphiphilic supramolecular polymer (ASP) with rigid linear main chain has been constructed by the co-assembly of a rigid amphiphilic monomer and cucurbit[8]uril (CB[8]) in water, driven by CB[8]-based host-guest interactions. The ASP could further self-assemble into well-defined architectures including nanotubes and 2D films, depending on its concentration. Moreover, pH-responsive behavior of the ASP was also observed.     

Hierarchical self-assembly of 3D amphiphilic discrete organoplatinum(Ⅱ)metallacage in water

Here we described the design and synthesis of a discrete 3D amphiphilic metallacage 4,in which the tetragonal prismatic frameworks act as the hydrophobic cores and the poly(ethylene glycol)(PEG)chains as the hydrophilic tails.The structure of 4 was characterized by 1H NMR,31P NMR and electrospray ionization time-of-flight mass spectrometry(ESI-TOF-MS).Notably,4 with its Iong PEG tails was subsequently ordered into micelles at a low concentration(1.20×10^-6 mol/L)in water.As the concentration and cultivation time increased,the micelles can further self-assembly into nanofibers and nanoribbons.Considering the dynamic property of the coordination bond,these structures show reversible transformation under external stimuli.     

Studies on the self-assembly behavior of the amphiphilic block copolymer of PSt-b-PAA in apolar solvents with polar fluorescent probe

The block copolymer of polystyrene-b-poly(butyl acrylate) (PSt-b-PBA) with a well-defined structure was synthesized by atom transfer radical polymerization (ATRP); its structure was characterized, and the living polymerization was also validated by gel permeation chromatography, Fourier transform infrared, and ¹H NMR measurements. Then, the amphiphilic block copolymer of polystyrene-b-poly(acrylic acid) (PSt-b-PAA) has been prepared by hydrolysis of PSt-b-PBA, and copolymers of PSt-b-PAA with longer PSt blocks and shorter PAA blocks were obtained by controlling the conditions of ATRP polymerization. The reversed micelle solution of PSt-b-PAA in toluene was prepared by using the single-solvent dissolving method, and the reverse micellization behavior of PSt-b-PAA in toluene was mainly investigated in this paper. The fluorescent probe technique was used by using polar fluorescence compound N-(1-Naphthyl)ethylenediamine dihydrochloride (NEAH) as a polar fluorescent probe to study the reverse micellization behavior of PSt-b-PAA. It was found that the reverse micellization behaviors of PSt-b-PAA in toluene can be clearly revealed by using NEAH as a polar fluorescence probe, and the critical micelle concentrations (cmcs) can be well displayed. The experimental results showed that the self-assembling behavior of PSt-b-PAA in toluene depends apparently on the microstructure of the macromolecules and is also influenced by the temperature. For the copolymers of PSt-b-PAA with the same length of hydrophobic PSt blocks, the copolymer with a longer hydrophilic block PAA has lower cmc, and at higher temperature, the copolymer has lower cmc.     

Progress and trends in self-assembly driven fluorescent organic nanoparticles: A brief overview

Organic nanoparticles have recently attracted increasing attention in diverse field of applications in materials, sensing, biomedicine and others due to their extraordinary physico-optical properties and facile synthesis. These π-conjugated small organic molecules exhibit aggregation induced emission (AIE) property, photo/physical stability, good cytocompatibility as well as biodegradability and easy surface modulation ability. In this mini-review, we have summarized the progress and trends in the area of development of organic nanoparticles from π-conjugated small organic molecule. Some typical as well as few unconventional examples of AIE active systems are discussed and also focussed on their structure-property relationship to exhibit unique photophysical characteristics. To decipher the mechanistic aspect of AIE phenomenon, systematic structural design strategies are also discussed. Finally, development of optoelectronic devices, sensors, bioimaging probes, therapeutic agents, and AIE-active luminogens are exemplified with high tech innovations.     

Synthesis of pH-responsive amphiphilic diblock copolymers containing polyisobutylene via oxyanion-initiated polymerization and their multiple self-assembly morphologies

 Two pH-responsive amphiphilic diblock copolymers, namely polyisobutylene-block-poly[2-(N,N-dimethylamino)ethyl methacrylate] (PIB-b-PDMAEMA) and polyisobutylene-block-poly(metharylic acid) (PIB-b-PMAA), were synthesized via oxyanion-initiated polymerization, and their multiple self-assembly behaviors have been studied. An exo-olefin-terminated highly reactive polyisobutylene (HRPIB) was first changed to hydroxyl-terminated PIB (PIB-OH) via hydroboration-oxidation of C＝C double bond in the chain end, and then reacted with KH to yield a potassium alcoholate of PIB (PIB-O^-K⁺). PIB-O^-K⁺ was immediately used as a macroinitiator to polymerize DMAEMA monomer, resulting in a cationic diblock copolymer PIB-b-PDMAEMA. With the similar synthesis procedure, the anionic diblock copolymer PIB-b-PMAA could be prepared via a combination of oxyanion-initiated polymerization of tert-butyl methacrylate (tBMA) and subsequent hydrolysis of tert-butyl ester groups in PtBMA block. The functional PIB and block copolymers have been fully characterized by ¹H-NMR, FT-IR spectroscopy, and gel permeation chromatography (GPC). These samples allowed us to systematically investigate the effects of block composition on the pH responsivity and various self-assembled morphologies of the copolymers in THF/water mixed solvent. Transmission electron microscopy (TEM) images revealed that these diblock copolymers containing small amount of original PIB without exo-olefin-terminated group are able to self-assemble into micelles, vesicles with different particle sizes and cylindrical aggregates, depending on various factors including block copolymer composition, solvent polarity and pH value.     

The amphiphilic multiarm copolymers based on hyperbranched polyester and lysine: Synthesis and self-assembly

The amphiphilic multiarm copolymers were synthesized through the modification of commercially available hyperbranched polyesters(Boltorn H40) with N-ε-carbobenzoxy-L-Lysine N-carboxyanhydride(ZLys-NCA).After being condensed with N-Boc-phenylalanine(Boc-~NPhe) and deprotected the Boc-groups in trifluoroacetic acid(TFA),the original terminal hydroxyl groups were transformed into the amino groups and then initiated the ring-opening polymerization of ZLys-NCA.The hydrophilic poly(L-lysine) was grafted to the surface of Boltorn H40 successfully after the protecting benzyl groups were removed by the HBr solution in glacial acetic acid(33 wt%).The resulting multiarm copolymers were characterized by the ~1H-NMR,GPC and FTIR.The arm length calculated by NMR and GPC analysis was about 3 and 13 lysine-units for H40-Phe-PLysl and H40-Phe-PLys2 respectively.Due to the amphiphilic molecular structure,they displayed ability to self-assemble into spherical micelles in aqueous solution with the average diameter in the range from 70 nm to 250 nm.The CMC of H40-Phe-PLysl and H40-Phe-PLys2 was 0.013 mg/mL and 0.028 mg/mL,respectively, indicating that H40-Phe-PLysl with shorter arm length is easier to self-assemble than H40-Phe-PLys2 with longer arm length.     

Controllable self-assembly of parallel gold nanorod clusters by DNA origami

We demonstrate the self-assembly of three types of parallel gold nanorod clusters using a rod-like DNA origami as the template.     

Synthesis, characterization and self-assembly of ion-bonded amphiphilic A2B miktoarm star copolymers containing an azobenzene unit at the core

An azobenzene-containing supramolecular copolymers, consisted of two polystyrene (PSt) arms and one poly(ethylene oxide) (PEO) arm linked via ionic bond, has been designed and successfully synthesized. Monomethoxy PEO with phenylazobenzenesulfonic acid as the terminus (PEO-NN-SO₃H) was utilized to react with polystyrene carrying tertiary amino group at the middle of the polymer chain (PSt₂-N(CH₃)₂) to form ion-bonded supramolecular star copolymers (PSt₂-NN-PEO) with an azobenzene group at the core based on the interaction between sulfonic acid group and amino group. The obtained copolymers were characterized by ¹H nuclear magnetic resonance (¹H NMR) and gel permeation chromatography (GPC) techniques. The self-assembly behavior of the copolymers with different molecular weight of PSt was investigated, which shows solid spherical aggregates in water. The aggregation leads to the lower isomerization degree (54%) at the photostationary state in water compared with that in 1,4-dioxane (82%).     

Binary self-assembly of highly symmetric DNA nanocages via sticky-end engineering

Discrete and symmetric three-dimensional(3D)DNA nanocages have been revoked as excellent candidates for various applications,such as guest component encapsulation and organization(e.g.dye molecules,proteins,inorganic nanoparticles,etc.)to construct new materials and devices.To date,a large variety of DNA nanocages has been synthesized through assembling small individual DNA motifs into predesigned structures in a bottom-up fashion.Most of them rely on the assembly using multiple copies of single type of motifs and a few sophisticated nanostructures have been engineered by co-assembling multi-types of DNA tiles simultaneously.However,the availability of complex DNA nanocages is still limited.Herein,we demonstrate that highly symmetric DNA nanocages consisted of binary DNA point-star motifs can be easily assembled by deliberately engineering the sticky-end interaction between the component building blocks.As such,DNA nanocages with new geometries,including elongated tetrahedron(E-TET),rhombic dodecahedron(R-DOD),and rhombic triacontahedron(R-TRI)are successfully synthesized.Moreover,their design principle,assembly process,and structural features are revealed by polyacryalmide gel electrophoresis(PAGE),atomic force microscope(AFM)imaging,and cryogenic transmission electron microscope imaging(cryo-TEM)associated with single particle reconstruction.     

Synthesis,self-assembly and photo-responsive behavior of AB2 shaped amphiphilic azo block copolymer

In this work, we report the synthesis of AB2 shaped amphiphilic azo block copolymer by macromolecular azo coupling reaction. The product and intermediates were characterized by various methods. The selfassembly in selected solvents and photo-responsive behavior of the copolymer were studied by means of UV–vis spectrophotometry and TEM. Spherical aggregates can be obtained by gradually adding water into the solution of this amphiphilic azo block copolymer. Upon irradiation with polarized UV(365 nm)light, the aggregates can be elongated in the polarized direction.     

Evidence of impurities in thiolated single-stranded DNA oligomers and their effect on DNA self-assembly on gold

The diversity of techniques used in the synthesis, treatment, and purification of the single-stranded DNA oligomers containing a thiol anchor group (SH-ssDNA) has led to a significant variation in the purity of commercially available SH-ssDNA. In this work, we use X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) to study how the impurities present in commercially synthesized SH-ssDNA oligomers affected the structure of the resulting DNA films on Au. XPS results indicate that two of the purchased SH-ssDNA oligomers contain excess carbon and sulfur. The molecular fragmentation patterns obtained with ToF-SIMS were used to determine the identity of several contaminants in the DNA films, including poly(dimethylsiloxane) (PDMS), lipid molecules, and sulfur-containing molecules. In particular, the ToF-SIMS results determined that the excess sulfur detected by XPS was due to the presence of dithiothreitol, a reductant often used to cleave disulfide precursors. Furthermore, we found that the SH-ssDNA self-assembly process is affected by the presence of these contaminants. When relatively pure SH-ssDNA is used to prepare the DNA films, the P, N, O, and C atomic percentages were observed by XPS to increase over a 24-h time period. In contrast, surfaces prepared using SH-ssDNA containing higher levels of contaminants did not follow this trend. XPS result indicates that, after the initial SH-ssDNA adsorption, the remaining material incorporated into these films was due to contamination.