Fabrication of cage-like particles via unstable seeded dispersion polymerization: A new concept in the polymerization-induced self-assembly

The formation mechanism of hollow micron-sized polystyrene (PS) particles having numerous dents on the surface, so-called cage-like particles, obtained from seeded dispersion polymerization (SDP) of 2-ethylhexyl methacrylate (EHMA) with low molecular weight (MW) PS particles stabilized by poly(vinyl alcohol) (PVA) in the presence of hexadecane droplets was investigated. It was found that association of poly(2-ethylhexyl methacrylate) (PEHMA)/hexadecane phases which occurs due to the instability of the obtained composite particles followed by a diffusion of PS ellipsoidal particles into each other is the main process responsible for the production of such unique morphology. Time course monitoring of the SDP showed that diffusion of hexadecane and/or PS and/or PEHMA phase into PS/PEHMA/hexadecane composite particles through PS shell which happens based on Ostwald ripening is the main phenomenon which results in the formation of the dents on the surface of final particles. Moreover, the experimental results revealed that in this reaction system, the polymerization develops in a faster manner rather than the SDP employing seed particles having higher MWs. Furthermore, it was observed that particles with different surface morphologies can be produced by using different hydrocarbons. The elimination of small particles which are produced in addition to the cage-like ones via decreasing the concentration of the stabilizer was another interesting finding of this research. The acquired results showed that unstable SDP is expected to be a new concept in polymerization-induced self-assembly (PISA) which employs instability of a dispersion for self-assembly of polymeric particles, and therefore, production of polymeric unique objects.     

Self-Assembly of Inorganic Nanocrystals: Emergence of a New Physics

In this paper we demonstrate that ordering of nanocrystals on long distance in 3D superlatices called supra crystals permit to emerge of collective intrinsic properties, which was not expected. The shape of the organization at the mesoscopic scale also induces new physical properties.     

开环聚合诱导自组装的挑战与展望

聚合诱导自组装（PISA）是一种新兴的纳米粒子制备技术,它集聚合与组装过程于一体,可在高固含量条件下进行,因此备受青睐.此外,通过改变嵌段聚合度以及固含量等参数,可以精确地控制纳米粒子的形貌,实现从球形胶束到空心囊泡的形貌转变.然而,受限于适用于PISA体系的聚合方法和单体种类,其发展也受到了一定的限制.目前,PISA主要基于可逆加成-断裂链转移聚合（RAFT）,其在聚合诱导自组装机理、形貌控制、结构表征等方面的研究成果,对于高分子化学其他领域具有重要的参考价值.然而,由于RAFT聚合诱导自组装（RAFT-PISA）体系中适用的单体往往局限于（甲基）丙烯酸酯类和苯乙烯类,导致RAFT-PISA制备的纳米粒子限于其碳-碳主链的基本结构难以生物降解,因此生物医用前景并不乐观.为了克服以上缺陷,开环聚合诱导自组装（ROPISA）应运而生,主要包括开环易位聚合诱导自组装（ROMPISA）、氨基酸-N-羧基-环内酸酐开环聚合诱导自组装（NCA-PISA）及自由基开环聚合诱导自组装（rROPISA）.由于ROMPISA体系对诸多功能性基团表现出化学惰性,从而为多功能纳米粒子的原位制备提供了新的方法;而rROPISA和NCA-PISA则使得生物可降解纳米粒子的原位制备成为可能.作为PISA领域崭新的研究方向,ROPISA不仅将新聚合方法引入了PISA体系,而且突破了以往PISA难以制备可降解纳米粒子的瓶颈,为PISA技术在生物医药领域的应用架起了桥梁.作者简要总结了ROPISA的发展现状,着重分析并提出了该领域面临的挑战,最后从机理研究、单体设计及转化应用等方面对ROPISA的发展前景进行了展望.     

来自化学前沿的挑战:动态自组装

分析了自组装的基本概念,指出动态自组装是化学前沿最具挑战性的问题之一,剖析了动态自组装研究的困难所在,在此基础上讨论了研究动态自组装的基本思路.     

Dynamic Complex‐to‐Complex Transformations of Heterobimetallic Systems Influence the Cage Structure or Spin State of Iron(II) Ions

Two new heterobimetallic cages, a trigonal‐bipyramidal and a cubic one, were assembled from the same mononuclear metalloligand by adopting the molecular library approach, using iron(II) and palladium(II) building blocks. The ligand system was designed to readily assemble through subcomponent self‐assembly. It allowed the introduction of steric strain at the iron(II) centres, which stabilizes its paramagnetic high‐spin state. This steric strain was utilized to drive dynamic complex‐to‐complex transformations with both the metalloligand and heterobimetallic cages. Addition of sterically less crowded subcomponents as a chemical stimulus transformed all complexes to their previously reported low‐spin analogues. The metalloligand and bipyramid incorporated the new building block more readily than the cubic cage, probably because the geometric structure of the sterically crowded metalloligand favours the cube formation. Furthermore it was possible to provoke structural transformations upon addition of more favourable chelating ligands, converting the cubic structures into bipyramidal ones.     

特殊纳米结构的化学自组装

本文介绍了近年来国际上一维纳米材料的制备方法的最近进展，如模板法、激光剥蚀法、分子束外延法、有机溶剂中溶液-液体-固体生长法等，同时还介绍了利用新的化学自组装路线制备一维核／鞘结构、无机半导体／高分子纳米电线、金属硫化物纳米空球和花生状纳米结构等工作。     

Dynamic Self‐Assembly of Gold/Polymer Nanocomposites: pH‐Encoded Switching between 1D Nanowires and 3D Nanosponges

The design of tunable dynamic self‐assembly of nanoparticles with switchable assembled dimensions and morphologies is a challenging goal whose realization is vital for the evolution of smart nanomaterials. Herein, we report on chitosan polymer as an effective supramolecular “glue” for aldehyde‐modified Au nanoparticles to reversibly modulate the states of self‐assembled nanocomposites. By simultaneous integration of dynamic covalent Schiff base interactions and noncovalent hydrogen bonds, the chitosan/Au nanocomposites could reversibly transform their assembled morphologies from one‐dimensional nanowires to three‐dimensional nanosponges in response to the variation of pH value. Moreover, the obtained nanosponges could be used as an efficient pH‐controlled cargo release system.     

聚电解质微球多级自组装制备双重药物载体

将表面带正电荷的壳聚糖(CS)微球和表面带负电荷的聚(L-谷氨酸)-b-聚氧化丙烯-b-聚(L-谷氨酸)(GPG)胶束共混,制备了CS/GPG聚集体水溶液体系.通过改变CS/GPG的共混比例,研究了CS微球和GPG胶柬形成稳定CS/GPG聚集体水溶液体系的配比范围,并对其粒径分布和表面电位进行了表征.在此基础上,将CS...     

金属卟啉配合物超分子自组装

介绍了金属卟啉配合物超分子自组装的基本方法和电子给-受体仿生超分子的研究；对金属卟啉配合物超分子自组装研究的发展方向进行了探讨。     

Emergent Self-Assembly Pathways to Multidimensional Hierarchical Assemblies using a Hetero-Seeding Approach

The controlled formation of complex and functional 1-, 2-, and 3D hierarchical assemblies from molecular building blocks represents a key current challenge. Herein, we report the use of a seeded growth approach for a series of perylenediimide-based molecules (PDIs 1 – 4 ) to access otherwise inaccessible self-assembly pathways that yield complex hierarchical structures. The key to the new approach is to use hetero-seeds which possess a different composition and morphology from that of the molecular building block. For example, a nanotube seed (from PDI 3 ) and a microribbon seed (from PDI 4 ) were found to initiate different self-assembly pathways for PDI 1 , which normally assembles to yield nanocoils. This led to the formation of unprecedented 3D scroll-like and scarf-like hierarchical nanostructures, respectively. Also, the hetero-seeds from PDI 3 initiate hidden self-assembly pathways of PDI 2 to generate 1D tubular heterojunctions. Significantly, this new strategy offers new opportunities to create emergent and functional hierarchical and complex structures from small molecule precursors.     

Controlled Self-Assembly of Metallacycle-Bridged Gold Nanoparticles for Surface-Enhanced Raman Scattering

In this work, well-defined two-dimensional metallacycles have been successfully employed for the well-controlled self-assembly of gold nanoparticles (AuNPs) into discrete clusters such as dimers, trimers, tetramers, pentamers and even hexamers at the water–oil interface for the first time. Furthermore, the modular construction of metallacycle molecules allows precise control of spacing between the gold nanoparticles. Interestingly, it was found that interparticle spacing below 5 nm created by molecular metallacycles in the resultant discrete gold nanoparticle clusters led to a strong plasmon coupling, thus inducing great field enhancement inside the gap between the NPs. More importantly, different discrete clusters with precise interparticle spacing provide a well-defined system for studying the hot-spot phenomenon in surface-enhanced Raman scattering (SERS); this revealed that the SERS effects were closely related to the interparticle spacing.     

Hierarchical self-assembly of triangular metallodendrimers into the ordered nanostructures

We designed and constructed a new family of 608 dendritic dipyridyl donors, from which two novel triangular metallodendrimers were successfully prepared via coordination-driven self-assembly.Inspired by the existence of multiple intermolecular interactions(e.g., p–p stacking and CH–p interactions) imposed by the DMIP-functionalized poly(benzyl ether) dendrons, their hierarchical selfassembly behaviors were studied in various mixed solvents by using scanning electron microscopy(SEM). Interestingly, it was found that the morphologies of the obtained metallodendrimers were highly depended on the dendron generation. For example, the first-generation metallodendrimer was able to hierarchically self-assemble into the spherical nanostructures in various mixed solvents. However, the nanofibers were observed for the second-generation metallodendrimer under the similar conditions.Furthermore, the driven force for the formation of such ordered nanostructures was investigated by using1 H NMR and fluorescence spectroscopy.     

Molecular design of supramolecular polymers with chelated units and their application as functional materials

This article summarizes the basic concepts and synthetic strategies leading to various types of supramolecular polymers with chelated units, including linear, branched, cross-linked, and heterometallic polymers. Particular attention is paid to such new synthetic approaches to supramolecular polymers as hierarchical and orthogonal self-assembly based on a combination of metal–ligand interaction with hydrogen bonds and host–guest interactions. Metallosupramolecular polyelectrolytes, supramolecular polymer gels, self-assembled metallosupramolecular monolayers, and supramolecular metal chelate dendrimers are analyzed. The stimuli-responsive, self-healing, and shape memory supramolecular polymers with chelated units are considered. The bibliography includes articles published over the past five years.     

A 2-Fold Interpenetrated Framework Assembled from Pyridine-3-carboxylate Ligand and Transition Metal:Synthesis,Structure and Photoluminescent Property

A novel cadmium（Ⅱ） coordination polymer [Cd2（3-pa）4（4,4＇-bpy）（H2O）].3.08H2O 1 has been synthesized by pyridine-3-carboxylate （3-pall） and CdO with exo-bidentate rigid dipyridyl ligand 4,4＇-bipyridine （4,4＇-bpy） by using a hydrothermal method, its structure was determined by single-crystal X-ray diffraction and its luminescent property was also documented. Complex 1 crystallizes in orthorhombic space group Pbcn with a = 21.4074（14）, b = 27.1119（18）, c = 12.3879（8） A, V = 7189.9（8） A3, Z = 8, C34H32.16Cd2N6O12.08, Mr= 942.85, Dc = 1.742 g/cms, p = 1.255 mm-1 and F（000） = 3766. The structure was solved by direct methods and refined to R = 0.0353 and wR = 0.0891 for 6278 observed reflections （I 〉 2σ（I））. The most prominent structural feature is the mutual interpenetration of two identical 3-D open frameworks via filling the large void space, which gives a 2-fold interpenetrating architecture during the self-assembly process.     

Heterotypic Supramolecular Hydrogels Formed by Noncovalent Interactions in Inflammasomes

The advance of structural biology has revealed numerous noncovalent interactions between peptide sequences in protein structures, but such information is less explored for developing peptide materials. Here we report the formation of heterotypic peptide hydrogels by the two binding motifs revealed by the structures of an inflammasome. Specifically, conjugating a self-assembling motif to the positively or negatively charged peptide sequence from the ASCPYD filaments of inflammasome produces the solutions of the peptides. The addition of the peptides of the oppositely charged and complementary peptides to the corresponding peptide solution produces the heterotypic hydrogels. Rheology measurement shows that ratios of the complementary peptides affect the viscoelasticity of the resulted hydrogel. Circular dichroism indicates that the addition of the complementary peptides results in electrostatic interactions that modulate self-assembly. Transmission electron microscopy reveals that the ratio of the complementary peptides controls the morphology of the heterotypic peptide assemblies. This work illustrates a rational, biomimetic approach that uses the structural information from the protein data base (PDB) for developing heterotypic peptide materials via self-assembly.     

Self-Assembled Nanotubes in Organic Solvents

Self-assembled nanotubes are formed spontaneously in alkane solvents by a simple diamide compound: the 3,5-Bis-(5-hexylcarbamoyl-pentyloxy)-benzoic acid decyl ester (BHPB-10). The tubular shape was proved by freeze fracture TEM and by SANS techniques. The tubes have a mean radius of 121 Å and a length of the order of a micron. BHPB-14, a homologue of this compound, bearing a longer ester chain (C14 instead of C10), self-assemble into flat ribbons under the same conditions. FTIR and UV spectroscopy showed that H-bonds between amide groups and π-π interaction between aromatic groups are involved in both kinds of aggregates and in the solid state as well. The nanotubes feature specific interactions between the ester carbonyls. Hence we show that ester, by its length and by the interactions between carbonyls determines the formation of nanotubes.     

Assembly of peptide–thiophene conjugates: the influence of peptide content and location

Biomolecule-directed self-assembly of π-conjugated oligomers has attracted great attention in the past decade. In this contribution, two conjugates composed of quaterthiophene and tetrapeptide (Gly-Val-Gly-Val) were synthesised, namely peptide–thiophene–peptide (PTP) and thiophene–peptide–thiophene (TPT), to investigate the influence of peptide content ratio and its location in the molecular structures on the nanostructures and properties of the assemblies. Both conjugates formed organogels consisting of left-handed twisted nanostructures; however, anti-parallel β-sheets were observed in PTP while parallel β-sheets were obtained for TPT, although in both cases oligothiophenes adopted an H-like stacking mode. Obvious solvent-induced supramolecular chirality inversion from the oligothiophene segment was observed for PTP while such phenomenon was not clear for TPT. PTP and TPT gels also showed different stabilities towards temperature increase, as evidenced by variable-temperature circular dichroism study. From the data, it is suggested that the rational design of the location and ratio of peptide plays a key role in constructing materials with determined properties based on peptide–thiophene conjugates.     

Controllable self-assemblies of β-cyclodextrin-calix[4]arene couples

Amphiphilic cyclodextrin-calixarene conjugates 1 and 2 were synthesized from "click chemistry", and their self-assembly behaviors were investigated by transmission electron microscopy, and atomic force microscopy. The results obtained show that 1 and 2 can self-assemble to form distinctly different aggregations, and the morphology of aggregations critically relies on the polarity and hydrophilicity of the solvent.     

分子结构对硫脲类化合物在铜表面自组装能力的影响

利用电化学阻抗谱和极化曲线研究了硫脲、烯丙基硫脲、苯基硫脲在金属铜表面上的自组装膜的质量和缓蚀效率, 并通过量子化学计算进一步研究了各种分子和金属铜的相互作用. 结果表明硫脲类分子在金属铜表面上的成膜能力顺序为: 苯基硫脲＞烯丙基硫脲＞硫脲, 并揭示了分子结构对硫脲类化合物在金属铜表面自组装影响的本质, 为进一步寻找和制备优良的缓蚀功能自组装膜提供理论依据.