嵌段共聚物自组装的研究进展

自组装是分子间通过非共价键相互作用自发组合形成的一类结构明确、稳定,同时具有某种特定功能或性能的分子聚集体或超分子结构的现象.嵌段共聚物不仅可以在本体中自组装,还能在溶液中自组装.本文综述了嵌段共聚物在溶液中自组装的规律及其主要影响因素,包括嵌段共聚物链段长度、选择性溶剂的性质、嵌段共聚物的浓度、溶液的pH值等;并介绍...     

单一分子量含氟嵌段共聚物的本体及薄膜自组装研究

嵌段共聚物导向自组装作为一种自下而上的图案化工艺,受到工业界和学术界的广泛关注.然而,导向自组装中缺陷率与分子参数之间的关系研究尚不清晰.本文工作基于模块化合成策略,利用迭代指数增长法并结合巯基-双键的点击反应成功制备了高χ低N的单一分子量含氟聚酯嵌段共聚物(oLA_n-FPOSS).单一分子量特征可以排除多分散性对自组装行为的影响.本体自组装研究表明聚酯嵌段和含氟嵌段具有强相分离驱动力,可以形成特征尺寸小于10 nm的六方柱状相结构(HEX).在薄膜自组装中,嵌段共聚物经过简单的热退火可以在硅片表面形成平行基底排布的柱状纳米图案.此外,通过对比研究不同链长单一分子量嵌段共聚物的薄膜组装行为,发现随着嵌段共聚物链长的增长薄膜组装图形缺陷率明显下降,初步揭示了薄膜自组装过程中缺陷形成对嵌段共聚物链长的依赖性.     

嵌段共聚物三维软受限自组装

嵌段共聚物在三维软受限条件下能够组装形成结构有序的聚合物胶束,其在催化、电子器件、光学传感等领域有广泛的应用价值,已经引起了广大科研工作者的关注。众所周知,嵌段共聚物自身性质及组装体内部结构和外部形状都会显著影响嵌段共聚物组装体性质及应用。本文简述了近年来嵌段共聚物三维软受限自组装的方法,分析了影响嵌段共聚物组装结构的内在和外在因素,内在因素主要指嵌段共聚物自身性质,包括嵌段共聚物种类、分子量及嵌段比;外在因素主要包括受限空间尺寸、界面性质、热或溶剂退火等。本文讨论了无机纳米粒子与嵌段共聚物三维软受限共组装,探讨了纳米粒子引入对组装结构影响及其在嵌段共聚物组装体中的分布及排列规律,以及组装结构的潜在应用。最后还讨论了目前嵌段共聚物三维软受限自组装存在的问题,同时对未来的发展方向进行了展望。     

两亲性/双疏性嵌段共聚物共混体系的自组装行为研究

采用耗散粒子动力学方法,研究了两亲性嵌段共聚物和双疏性嵌段共聚物共混体系的自组装行为,探讨了双疏性嵌段共聚物的浓度以及双疏性嵌段共聚物的嵌段体积分数对聚集体结构的影响.结果表明,随着双疏性嵌段共聚物浓度的增加,聚集体发生自囊泡到棒状胶束再到同心圆多舱胶束的转变,且当浓度较高时,同心圆多舱胶束的同心圆层数量与浓度密切相关.当双疏性嵌段共聚物中的嵌段体积分数降低时,球形胶束由同心圆结构转变为非同心圆结构.此外,利用Minkowski泛函方法表征了多舱胶束的形成过程,发现这是一个先形成大尺度球形结构、再形成小尺度内核结构的分级组装过程.     

嵌段共聚物纳米结构设计的计算机模拟研究

嵌段共聚物在本体或在选择性溶剂中可以通过微相分离或自组装形成各种各样的纳米结构,如层状相、球状、棒状及碟状胶束、双层膜、囊泡、纳米管等.这些纳米结构在药物输送、微电子学、先进材料等领域具有令人瞩目的应用前景.因此,研究嵌段共聚物形成纳米有序结构的过程以及理解复杂纳米结构的形成机理具有非常重要的意义.由于嵌段共聚物纳米聚...     

ABC型嵌段共聚物自组装理论研究进展

嵌段共聚物的自组装为功能性纳米材料的制备提供了一种重要途径. ABC型嵌段共聚物相比于AB型具有更大的参数空间,自组装行为也更加复杂.在实验所合成的三组分嵌段共聚物自组装体系中,已有多种复杂结构被发现,如螺旋超柱、编织图案等,但实验上比较难以直接阐明它们的形成机理.近年来,本课题组运用自洽场理论(SCFT)对ABC型嵌段共聚物自组装进行了系统的研究,聚焦探索其结构参数及拓扑结构对相行为的影响机制.本文介绍了本课题组关于“非受挫”和“受挫”两大类ABC型嵌段共聚物自组装的SCFT研究成果,揭示了一些非经典相的形成机理,并通过合理的分子设计预测了一系列新颖的有序结构.     

偶氮液晶嵌段共聚物自组装和光响应性研究进展

偶氮液晶嵌段共聚物是指分子中带有偶氮苯基团的液晶嵌段共聚物.偶氮液晶嵌段共聚物兼具偶氮聚合物的光响应性和液晶嵌段共聚物自组装形成多尺度有序结构的特性,是一类有重要应用前景的新材料.本文简要综述了近10年来偶氮液晶嵌段共聚物的研究进展,以几种典型的偶氮液晶嵌段共聚物为例,介绍嵌段共聚物在本体以及溶液状态下自组装,自组装形貌的光致变化,以及偶氮液晶嵌段共聚物在光全息存储领域等的研究进展.     

本体柱状的线形嵌段共聚物在受限状态下的自组装结构

综述了使用计算机模拟方法研究在本体状态下形成柱状结构的线形二嵌段和三嵌段共聚物在平行板间和纳米圆孔内的自组装结构.研究发现,嵌段共聚物体系在受限状态下自组装可以得到与本体状态下不同的纳米结构,调整受限状态的物理化学性质可以调控受限体系的相行为,从而诱导体系形成特定的结构.模拟研究还发现不同相分离强度和链结构的体系,在相同的受限状态下表现出不同的相行为.因此在制备纳米结构材料的研究中,人们要根据嵌段共聚物体系的特定性质,选择相应的受限环境,才能够实现有效的控制.     

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.     

中国嵌段共聚物受限自组装的研究进展

近年来,嵌段共聚物在受限空间中的自组装已成为高分子科学领域一个新的关注点.在受限条件下,嵌段共聚物展现出更多的可调控性,可获得复杂多样的微相分离结构.这些新颖的结构为实现嵌段共聚物更加丰富的功能奠定了材料基础.中国的学者们在嵌段共聚物受限自组装的理论模拟和实验研究方面取得了一系列重要创新成果,有力地推动了该领域的发展.本文总结和评述了中国学者在该领域的研究进展,并展望了嵌段共聚物受限自组装研究未来发展的机遇与挑战.     

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...     

Tandem interactions in the self-assembly of ionic block copolymers

The aim of the present review is to show how the phenomena of block copolymer self-assembly and interactions of ionic (or ionizable) groups in polymer systems can be combined to produce materials with versatile and unique behavior. In our discussion, we consider two classes of tandem interactions. First, block copolymers containing short ionic blocks and long nonionic blocks are investigated in organic media. In systems of this type, block copolymer self-assembly and short-range electrostatic interactions act in tandem, forming regular and highly-stable spherical structures. Next, we consider ionic (or ionizable) block copolymers dissolved in aqueous media. In this case, block copolymer self-assembly acts in tandem with the hydrophilic nature of the soluble blocks, resulting in a wide range of unique morphologies.     

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.     

Toughness Properties of Lightly Crosslinked Epoxies Using Block Copolymers

Summary: In this work is discussed an alternative approach to the toughening of epoxy networks by the addition of acrylic block copolymers, composed of rigid and rubbery blocks. Once the reaction is completed, the initial self-assembly of block copolymers in epoxy thermoset precursors produces rubbery domains: depending on the block copolymer structure and composition, these domains are of the micrometer or the nanometer size. Nanostructures are obtained when the rigid block is a random copolymer of methylmethacrylate and N,N-dimethylacrylamide. The rubbery domains prevent rapid crack propagation and the highest toughness is obtained with filament-like microparticles or wormlike micelles.     

Using polyelectrolyte block copolymers to tune nanostructure assembly

This review presents an overview of the recent developments in polyelectrolyte block copolymer self-assembly, including charged block copolymers and random copolymers as well as polypeptidic block copolymers. Different methods for controlling micellar structures in solution are presented. In addition, the use of polyelectrolyte copolymers as responsive hydrogels, in polyelectrolyte complexes, and in layer-by-layer assemblies will be discussed.     

Unexpected consequences of block polydispersity on the self-assembly of ABA triblock copolymers

Controlled/"living" polymerizations and tandem polymerization methodologies offer enticing opportunities to enchain a wide variety of monomers into new, functional block copolymer materials with unusual physical properties. However, the use of these synthetic methods often introduces nontrivial molecular weight polydispersities, a type of chain length heterogeneity, into one or more of the copolymer blocks. While the self-assembly behavior of monodisperse AB diblock and ABA triblock copolymers is both experimentally and theoretically well understood, the effects of broadening the copolymer molecular weight distribution on block copolymer phase behavior are less well-explored. We report the melt-phase self-assembly behavior of SBS triblock copolymers (S = poly(styrene) and B = poly(1,4-butadiene)) comprised of a broad polydispersity B block (M(w)/M(n) = 1.73-2.00) flanked by relatively narrow dispersity S blocks (M(w)/M(n) = 1.09-1.36), in order to identify the effects of chain length heterogeneity on block copolymer self-assembly. Based on synchrotron small-angle X-ray scattering and transmission electron microscopy analyses of seventeen SBS triblock copolymers with poly(1,4-butadiene) volume fractions 0.27 ≤ f(B) ≤ 0.82, we demonstrate that polydisperse SBS triblock copolymers self-assemble into periodic structures with unexpectedly enhanced stabilities that greatly exceed those of equivalent monodisperse copolymers. The unprecedented stabilities of these polydisperse microphase separated melts are discussed in the context of a complete morphology diagram for this system, which demonstrates that narrow dispersity copolymers are not required for periodic nanoscale assembly.     

Synthesis and Self-Assembly of Mixed-Graft Block Copolymers

Mixed-graft block copolymers (mGBCPs) consist of two or more types of polymeric side chains grafted on a linear backbone in a random, alternating, or pseudo-alternating sequence. They can phase-separate with the backbone serving as the interface of the blocks, and the side chains dominate their self-assembly behavior. mGBCPs are an accessible polymer architecture for exploring the idea of encoding polymer properties through the macromolecular architecture, as there are two distinct structural components that can be tuned: the backbone and the side chains. In this Concept article, the current literature on the synthesis of mGBCPs is reviewed, and the advantages and disadvantages of each synthetic method are noted. The self-assembly of mGBCPs is also discussed where possible. Finally, directions for future research on mGBCP synthesis and self-assembly are suggested.     

Effect of block length, polydispersity, and salt concentration on PEO-PDEAMA block copolymer structures in dilute solution

A series of poly(ethylene oxide)-block-poly(N,N-diethylaminoethyl methacrylate) (PEO-PDEAMA) block copolymers with relatively high polydispersity (1.36 < PDI < 1.96) have been prepared to determine the effect that polydispersity has on the self-assembly of amphiphilic block copolymers in dilute solution. Because monodisperse macroinitiators were used for the ATRP reactions, the polydispersity resides within the hydrophobic block. By adjusting the relative block lengths, spherical micelles, wormlike micelles, vesicles, or a precipitate is formed. Here, we show that relatively high polydispersity in the block copolymer does not preclude efficient self-assembly. We also discuss the effect of increasing the concentration of NaCl in the systems and show that this can result in a shift from one morphology to another. These shifts are reversible in some cases, but for PEO12-PDEAMA39, this method allows access to giant vesicles of between 500 nm and 1 microm in diameter.     

经两亲嵌段共聚物自组装制备纳米胶束

本文介绍两亲嵌段共聚物的合成,综述了经两亲嵌段共聚物自组装制备纳米胶束的研究进展,并对该领域的发展趋势进行了展望。