Cross-linked and functionalized ‘universal polymer backbones’ via simple, rapid, and orthogonal multi-site self-assembly

A novel route to cross-linked and functionalized random copolymers using a rapid, one-step, and orthogonal copolymer cross-linking/functionalization strategy has been developed. Random terpolymers possessing high concentrations of pendant alkyl chains and either (1) palladated-pincer complexes and diaminopyridine moieties (DAD hydrogen-bonding entities) or (2) palladated-pincer complexes and cyanuric wedges (ADAADA hydrogen-bonding entities) have been synthesized using ring-opening metathesis polymerization. Non-covalent cross-linking of the resultant copolymers using a directed functionalization strategy leads to dramatic increases in solution viscosities for cross-linked polymers via metal-coordination while only minor changes in viscosity were observed when hydrogen-bonding motifs were employed for cross-linking. The cross-linked materials could be further functionalized via self-assembly by employing the second recognition motif along the polymeric backbones giving rise to highly functionalized materials with tailored cross-links. This novel non-covalent polymer cross-linking/functionalization strategy allows for rapid and tunable materials synthesis by overcoming many difficulties inherent to the preparation of covalently cross-linked polymers.     

Self-assembly of Amphiphilic Alternating Copolymers

Polymer self-assembly has been a hot research topic for several decades. Different types of polymers with various architectures, like block copolymers, brush polymers, hyperbranched polymers and dendrimers, etc., are currently being investigated. Alternating copolymers (ACPs) are regular copolymers with an alternating monomeric unit structure in the polymer backbones. However, despite the great progress in the synthesis of ACPs, their self-assembly is still in an infant stage. Very recently, our group reported a new type of amphiphilic ACPs through click copolymerization and obtained spheres, vesicles, nanotubes, and even hierarchical sea urchin-like aggregates through the self-assembly process. In addition, we have found some intriguing features in the self-assembly of amphiphilic ACPs when compared with other copolymers, including their facile syntheses, readily functionalization, novel self-assembly structures, new folding-chain mechanisms, and uniform but ultrathin feature length. In this Concept article, we present the self-assembly of amphiphilic ACPs together with their unique features by reviewing our latest results and related studies. Moreover, the future perspective on the self-assembly of amphiphilic ACPs is also proposed. Our aim is to capture the attention and interest of chemists in this new area of polymerization.     

One-step synthesis of ordered mesoporous carbonaceous spheres by an aerosol-assisted self-assembly

Ordered mesoporous carbonaceous spheres with variable structures have been successfully prepared by using phenolic oligomers as a carbon precursor and amphiphilic triblock copolymers as a template via a one-step aerosol-assisted organic-organic self-assembly method.     

由嵌段共聚物制备有形状的核壳结构聚合物纳米颗粒

嵌段共聚物可自发组装形成形貌丰富的纳米粒子和有序纳米结构的材料,为纳米材料和纳米技术领域提供了很重要的新材料和新手段.该领域的进一步发展提出了对嵌段共聚物的自组装体赋予功能性的要求,即需要通过可控聚合反应合成反应性嵌段共聚物,并且对其自组装的纳米粒子进行结构、形状及功能性的调控.本文针对以上研究目标,结合本课题组在该领...     

Polyacrylamide conjugated with poly(oxyethylene)-block-poly(oxypropylene)-block-poly(oxyethylene): a self-assembling material

A novel one-step synthesis of hydrophobically modified polyacrylamide (PAAm) is described. Triblock copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PEO-PPO-PEO) are grafted onto PAAm in melts of acrylamide in the presence of benzoyl peroxide. The resulting PEO-PPO-PEO-g-PAAm graft copolymers are capable of self-assembly in response to temperature changes in aqueous media.     

Cyclodextrin-based inclusion complexation bridging supramolecular chemistry and macromolecular self-assembly

Research into macromolecular self-assembly has been progressively developing since the 1970s but with a little affect from the achievements of supramolecular chemistry. In recent years, this situation has changed as more and more factors and concepts in supramolecular chemistry have been introduced into studies of the self-assembly of polymers. In this respect, inclusion complexation based on cyclodextrins plays a remarkable role. In this tutorial review, we address how inclusion complexation has been employed and used to promote the recent developments in macromolecular self-assembly. These include the amphiphilicity adjustment of macromolecules, non-covalent linkages for forming pseudo block copolymers and micelles, surface modification and functionalization of polymeric micelles and vesicles, and the combination of synthetic polymeric assemblies with biological moieties. Furthermore, the realization of the reversible stimuli-responsiveness of polymeric assemblies and materials, particularly hydrogels by means of controllable inclusion complexation is discussed as well.     

Self-assembly with block copolymers through metal coordination of SCS-Pd(II) pincer complexes and pseudorotaxane formation

Poly(norbornene)-based block copolymers containing side chains of palladated pincer complexes/dibenzo[24]crown-8 or palladated pincer complexes/dibenzylammonium salts were synthesized. Noncovalent functionalization was accomplished with their corresponding recognition units through simple 1:1 addition with association constants (Ka) greater than 10(5) m(-1). The self-assembly processes were monitored by using both 1H NMR spectroscopy and isothermal titration calorimetry. In all cases, we found that the self-assembly of the recognition units along each polymer block does not preclude the self-assembly processes along the other block.     

Towards Targeted Drug Delivery by Covalent Ligand-Modified Polymeric Nanocontainers

Here we present a novel strategy for specific cellular targeting of polymeric nanocontainers by using self-assembly of block copolymers consisting of either Polydimethoxysiloxane-b-Polymethyloxazoline-b-Polydimethoxysiloxane (PDMS-b-PMOXA-b-PDMS) or functionalized PDMS-b-PMOXA-b-PDMS. Covalent functionalization of the above copolymer was accomplished using either the fluorescent dye sulforhodamine B or a poly-guanosin ligand, the latter by using the Huisgen 1,3-dipolar cycloaddition. The success of the covalent modification of the block copolymer has been determined by studying functionalized sulforhodamine B by NMR and fluorescence correlation spectroscopy. The covalent click chemistry approach leads to efficiently functionalized polymeric nanocontainers which enables specific uptake by activated macrophages overexpressing the scavenger receptor A1.     

有序介孔碳材料的软模板合成、结构改性与功能化

有序介孔碳材料在吸附、分离、催化以及能量存储/转化等方面具有广阔的应用前景。相较于复杂的硬模板路线,基于两亲性嵌段共聚物和聚合物前驱体间（如酚醛树脂）自组装的软模板路线是合成有序介孔碳材料更为有效的方法。本文讨论比较了溶剂挥发诱导自组装法、水相协同自组装法和无溶剂法等三种典型软模板路线的基本过程和特点,并介绍了近年来在新型碳前驱体应用、介孔碳的结构改性和功能化等方面的一些重要进展,最后总结了介孔碳的合成研究中所需解决的关键问题。     

Polyglucane derivatives with regular substituent distribution

6-O-trialkylsilyl celluloses, 2,3-O-carboxymethylcelluloses, cellulose-3-O-sulfate, and carboxymethylcellulose block copolymers were synthesized by regioselective functionalization of cellulose and of soluble cellulose intermediates like silyl and methoxy-substituted trityl ethers as well as formates and trifluoroacetates. The preparation and structure characterization (NMR, FTIR, HPLC after chain degradation) of those polyglucane derivatives with regular substituent distribution is of importance to design self-assembly systems and supramolecular structures (liquid-crystalline media, ultrathin films, recognition and bioactive materials).     

Self-assembled ordered polymer nanocomposites directed by attractive particles

We theoretically investigate general conditions under which an inorganic phase can direct the self-assembly of an ordered polymer nanocomposite. For this purpose, we consider a solution of triblock copolymers forming a hexagonal phase of micelles and investigate the effect of adding attractive particles. We show that if the triblock is functionalized at its ends by attaching groups with specific affinity for the particles, thus effectively becoming a pentablock, the particles direct the self-assembly of the system into phases where both the polymers and the particles exhibit mesoscopic order. Different lamellar and gyroid phases (both with Ia3d and I4(1)32 space symmetries) are presented in detail. Our results show that functionalization is a very powerful route for directing self-assembly of polymer nanocomposites. We briefly discuss the connections with recent theoretical and experimental results in diblock melts with nanoparticles as well as for problems where polymers are used to template the growth of an inorganic phase in solution.     

Phase diagrams,mechanisms and unique characteristics of alternating-structured polymer self-assembly via simulations

Alternating-structured polymers(ASPs), like alternating copolymers, regular multiblock copolymers and polycondensates, are very important polymer structures with broad applications in photoelectric materials. However, their self-assembly behaviors,especially the self-assembly of alternating copolymers, have not been clearly studied up to now. Meanwhile, the unique characteristics therein have not been systematically disclosed yet by both experiments and theories. Herein, we have performed a systematic simulation study on the self-assembly of ASPs with two coil alternating segments in solution through dissipative particle dynamics(DPD) simulations. Several morphological phase diagrams were constructed as functions of different impact parameters. Diverse self-assemblies were observed, including spherical micelles, micelle networks, worm-like micelles, disklike micelles, multimicelle aggregates, bicontinuous micelles, vesicles, nanotubes and channelized micelles. Furthermore, a morphological evolutionary roadmap for all these self-assemblies was constructed, along with which the detailed molecular packing models and self-assembly mechanisms for each aggregate were disclosed. The ASPs were found to adopt a folded-chain mechanism in the self-assemblies. Finally, the unique characteristics for the self-assembly of alternating copolymers were revealed especially, including(1) ultra-fine and uniform feature sizes of the aggregates;(2) independence of self-assembled structures from molecular weight and molecular weight distribution;(3) ultra-small unimolecular aggregates. We believe the current work is beneficial for understanding the self-assembly of alternating structured polymers in solution and can serve as a guide for the further experiments.     

Self-assembly of polypeptide-based copolymers into diverse aggregates

Recently, increasing attention has been given to the self-assembly behavior of polypeptide-based copolymers. Polypeptides can serve as either shell-forming or core-forming blocks in the formation of various aggregates. The solubility and rigidity of polypeptide blocks have been found to have a profound effect on the self-assembly behavior of polypeptide-based copolymers. Polypeptide graft copolymers combine the advantages of a grafting strategy and the characteristics of polypeptide chains and their self-assembly behavior can be easily adjusted by choosing different polymer chains and copolymer architectures. Fabricating hierarchical structures is one of the attractive topics of self-assembly research of polypeptide copolymers. These hierarchical structures are promising for use in preparing functional materials and, thus, attract increasing attention. Computer simulations have emerged as powerful tools to investigate the self-assembly behavior of polymers, such as polypeptides. These simulations not only support the experimental results, but also provide information that cannot be directly obtained from experiments. In this feature article, recent advances in both experimental and simulation studies for the self-assembly behavior of polypeptide-based copolymers are reviewed.     

High-Fidelity End-Functionalization of Poly(ethylene glycol) Using Stable and Potent Carbamate Linkages

Commercial PEG-amine is of unreliable quality, and conventional PEG functionalization relies on esterification and etherification steps, suffering from incomplete conversion, harsh reaction conditions, and functional-group incompatibility. To solve these challenges, we propose an efficient strategy for PEG functionalization with carbamate linkages. By fine-tuning terminal amine basicity, stable and high-fidelity PEG-amine with carbamate linkage was obtained, as seen from the clean MALDI-TOF MS pattern. The carbamate strategy was further applied to the synthesis of high-fidelity multi-functionalized PEG with varying reactive groups. Compared to with an ester linkage, amphiphilic PEG-PS block copolymers bearing carbamate junction linkage exhibits preferential self-assembly tendency into vesicles. Moreover, nanoparticles of the latter demonstrate higher drug loading efficiency, encapsulation stability against enzymatic hydrolysis, and improved in vivo retention at the tumor region.     

杂臂星型嵌段共聚物在溶液中自组装形成囊泡结构的计算机模拟

利用耗散粒子动力学模拟方法, 研究了杂臂星型嵌段共聚物A_m(B_n)₂在溶液中自组装形成囊泡的行为. 主要分析了自组装过程、亲水分枝和疏水分枝的长度及分子构型对组装结构的影响. 结果表明, 杂臂星型聚合物在溶液中会自组装形成碟状胶束, 之后弯曲闭合形成囊泡. 当亲水部分的分枝较短时, 易于形成囊泡结构; 在可形成囊泡结构的条件下, 双分子层囊泡膜的厚度随分枝长度的增加而增加. 与构成相近的线型嵌段共聚物相比, 杂臂星型嵌段共聚物更易形成囊泡结构, 且形成的囊泡结构较薄.     

Block Copolymer-Templated Synthesis and Organization of Semiconductor Nanocrystals

Summary: Templates formed by the self-assembly of amphiphilic block copolymers in selective solvents have been found to be instrumental in controlling critical parameters in semiconductor nanomaterials fabrication, including particle size, shape, and composition. These tunable nanoreactors exhibit rich polymorphism and have enabled the synthesis of a variety of nanostructures such as dots, wires, tubes, hollow spheres, and 2-D structures by growth-under-confinement at room temperature. The encapsulated particles have optical and electronic properties that are dependent upon physical dimensions and morphology, and exhibit inherent stability and functionalization flexibility, thus opening up promising prospects through their integration into functional optoelectronic and biological systems.     

Novel polyaminoacidic copolymers as nonviral gene vectors

 Human gene therapy is one of the most promising methods developed in recent years, providing great potential for the treatment of a variety of diseases. Complexes formed between DNA and cationic polymers are attracting increasing attention as novel synthetic vectors for the delivery of genes. We have synthesized polycations with quaternary ammonium groups in their side chains for self-assembly with calf thymus DNA. This paper describes the functionalization of α,β-polyasparthydrazide (PAHy), a synthetic macromolecule having many potential applications in the field of biomedical sciences, with glycidyltrimethylammonuim chloride (GTA) in order to introduce positive charges into their chains. Derivatized PAHy with various GTA contents have been obtained and characterized. Highly functionalized copolymers have been used for condensing DNA, yielding discrete complexes. The complex formation has been confirmed by gel electrophoresis and the surface charge of interpolyelectrolyte complexes has been assessed by the zeta potential. Received: 22 June 1999/Accepted in revised form: 17 August 1999     

两亲性Janus粒子在蜂窝状多孔聚合物膜上的自组装性能

采用具有两亲性的两面体(Janus)粒子实现稳定的粒子界面组装与水滴模板法自组装过程相结合的方法获得了粒子在蜂窝状多孔聚合物薄膜内壁的高效定向修饰.通过与均质粒子组装形貌的对比,证明了Janus粒子因其特殊的界面自组装活性,可以获得高粒子加量条件下的规则多孔结构,解决了使用均质粒子时存在的结构有序性和粒子修饰密度之间的矛盾.而在较低粒子加量的条件下,Janus粒子也展示出与均质粒子极为不同的组装形貌.这一方法的建立,为新型表面功能化材料的制备提供了一个新的思路.     

One-step selective chemistry for silicon-on-insulator sensor geometries

A one-step functionalization process has been developed for oxide-free channels of field effect transistor structures, enabling a self-selective grafting of receptor molecules on the device active area, while protecting the nonactive part from nonspecific attachment of target molecules. Characterization of the self-organized chemical process is performed on both Si(100) and SiO(2) surfaces by infrared and X-ray photoelectron spectroscopy, atomic force microscopy, and electrical measurements. This selective functionalization leads to structures with better chemical stability, reproducibility, and reliability than current SiO(2)-based devices using silane molecules.     

聚二茂铁基硅烷二嵌段共聚物的制备、组装及应用研究

二茂铁分子由于含有独特的芳香结构和过渡金属元素铁,具有特殊的光、电、磁特性,一直以来是科学研究和技术应用的热点之一,在功能高分子材料的制备方面具有广泛的应用前景。聚二茂铁硅烷嵌段共聚物是一类新型的主链含有二茂铁和有机硅单元的聚合物,以其可控的分子量和丰富的自组装形貌,不断得到科研人员的关注。本文主要从聚合、自组装和应用三个方面系统介绍了聚二茂铁硅烷二嵌段共聚物。其中重点介绍了应用广泛的活性阴离子聚合和进一步发展起来的阴离子两步法聚合,解释了活性聚合机理,归纳了目前成功合成的不同种类的二嵌段共聚物;论述了在选择性溶剂中,聚二茂铁硅烷二嵌段共聚物可以自组装形成柱状、管状、球状等常规胶束和片层、刷形等复杂胶束,胶束的形成同聚合一样具有活性特征,并且在一定的刺激条件下,不同类型的胶束可完成相互转变过程,另外可以对胶束局部进行功能化以赋予其特殊的性能;最后介绍了聚二茂铁硅烷二嵌段共聚物在药物缓释、纳米材料、特种催化方面的具体实例,并对其应用前景加以展望。