Robust control of microdomain orientation in thin films of block copolymers by zone casting

Block copolymers with chemically immiscible segments exhibit a variety of microphase-separated nanostructures on the scale of 10-100 nm. Controlling the orientation of these microphase separated nanostructures is vital in many applications such as lithography, membranes, data storage, and so forth. Typical strategies involve the use of external fields or patterned substrates. Here, we report a robust zone casting technique to achieve highly ordered thin films of block copolymers on centimeter-scale substrates. The robustness of this technique is its powerful control on diverse morphologies and exceptional tolerance on versatility of block copolymer chemistry as well as allowance of a wide spectrum of substrates. We demonstrate that perpendicular orientations with respect to the surface are achieved for block copolymers with both lamellar and cylindrical morphologies by controlling solution casting rate, temperatures, and block copolymer chemical structures. Thin films of both noncrystalline and crystalline block copolymers exhibit excellent orientational order and lateral order. However, the lateral order in the thin films of crystalline block copolymers shows dependence on casting temperature and melting temperature of the crystalline segment. Remarkably, all the ordering is independent of the substrates on which the block copolymer films are cast.     

Mesoscopic simulation of the self-organization of a binary mixture of copolymers in the vicinity of a selective adsorbing surface

A new strategy for the construction of ultrathin structured films with cylindrical microdomains oriented primarily perpendicularly to the surface of a solid substrate is proposed. This approach is based on the phase separation of a binary mixture of incompatible compositionally asymmetric block copolymers, microphase separation of their blocks, and selective adsorption of one of the copolymers on the surface. Preferentially adsorbed copolymer forms a regular pattern on the surface, which serves as an orienting support for another component that dominates in the system and forms the hexagonal mesophase in the bulk of the film. This approach has been verified by the mesoscopic simulation based on the dynamic version of the density functional theory. As a result of the self-organization of macromolecules, the morphology with perpendicularly oriented domains can be thermodynamically stable for the films with a thickness of ∼100 nm. The commensurability of the parameters of the surface pattern and volume mesophase is shown to be the key factor controlling the orientation of cylindrical microdomains.     

Synthesis, post-modification and self-assembled thin films of pentafluorostyrene containing block copolymers

Block copolymers consisting of a pentafluorostyrene (PFS) block and a hydrophilic block were synthesized by RAFT polymerisation. The hydrophilic blocks consist of methacrylate derivatives, 4-hydroxystyrene or 4-vinylpyridine monomers. The block copolymers were obtained with narrow molecular weight distributions and the molecular weights were in good agreement with the theoretical values. In addition, a model thiol was reacted with the PFS moieties of the block copolymers. This polymer–analogous reaction was performed under ambient conditions in high yields resulting quantitatively in para-substitution of the pentafluorophenyl rings. Finally, thin films consisting of block copolymers that showed strong phase-segregation behaviour and ordered nanostructured surfaces consisting of both blocks were obtained.     

Nanofabrication in Polymer Solutions

Nanostructured materials have drawn a great deal of attention in recent yearsbecause of their promising potentials in future applications.The fabrication of nano-materials has become a highly active research area involving scientists in many differentfields,e.g.,physics,chemistry,biology and materials science and engineering. Theinorganic synthesis including biomineralization by using intermolecular bonds to act in acooperative manner in order to construct organized supramolecular systems by s…     

Solvent-regulated ordering in block copolymers

Studies of the structural polymorphism exhibited by block copolymers in the presence of selective solvents are relatively recent, but very promising in terms of fundamental understanding and practical applications. Highlighting recent advances, this review progresses from `dry' ordered copolymers to solvated ordered (gel-like) copolymers and lastly to solvated disordered (but locally organized) copolymers. Organic- and aqueous-solvent-based systems are concurrently examined to cross-fertilize polymer and colloid science.     

Controlled Assembly of Block Copolymer Coated Nanoparticles in 2D Arrays

The defined assembly of nanoparticles (NPs) in polymer matrices is an important prerequisite for next‐generation functional materials. A promising approach to control NP positions in polymer matrices at the nanometer scale is the use of block copolymers. It allows the selective deposition of NPs in nanodomains, but the final defined and ordered positioning of the NPs within the domains has not been possible. This can now be achieved by coating NPs with block copolymers. The self‐assembly of block copolymer‐coated NPs directly leads to ordered microdomains containing ordered NP arrays with exactly one NP per unit cell. By variation of the grafting density, the inter‐nanoparticle distance can be controlled from direct NP surface contact to surface separations of several nanometers, determined by the thickness of the polymer shell. The method can be applied to a wide variety of block copolymers and NPs and is thus suitable for a broad range of applications.     

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...     

Effects of Sequence Distribution and Physical Aging on Physical Properties of PES/PEES Random, Block, and Alternative Copolymers

IntroductionPhysical aging involves spontaneous changes in thephysical properties of polymer glasses from its nonequi-librium state to the equilibrium state. Aging affectsseveral properties such as specific volume, enthalpy,and mechanical and dielectric r…     

两亲性嵌段共聚物PS-b-PMAA的合成与胶束化行为研究

利用原子转移自由基聚合法(ATRP)得到了分子量可控、分子量分布接近1.1的聚苯乙烯-b-聚甲基丙烯酸叔丁酯(PS-b-PtBMA)嵌段共聚物, 进而在酸性条件下由水解反应得到了两亲性的聚苯乙烯-b-聚甲基丙烯酸 (PS-b-PMAA)嵌段共聚物．用GPC, FTIR和¹H-NMR等对产物的分子量和组成进行了表征．使PS-b-PMAA在选择性溶剂中进行自组装, 通过激光光散射和透射电子显微镜研究了影响其胶束化行为的因素与胶束形态, 并初步探讨了胶束形成的机理, 发现通过控制嵌段共聚物的链段长度之比可得到空心球形的高分子胶束．     

嵌段共聚物薄膜在电化学能源领域的应用

采取选择性掺杂方法,将新型两亲性液晶嵌段共聚物薄膜功能化为具有各向异性的锂离子导电材料.这类薄膜不仅具有同轴且垂直取向的一维离子导电通道,而且可以在大面积范围内形成规则的阵列,可以作为锂离子电池、燃料电池等电化学能源系统的新型电解质.另一方面,这类薄膜作为模板可制备周期性排列的纳米孔、纳米粒子、纳米线阵列,形成的有序纳米结构材料可作为锂离子电池的三维电极.     

Morphologies and domain sizes of microphase-separated structures of block and graft copolymers of different types

Well-defined block and graft copolymers of different types with different compositions and molecular weights, such as styrene(S)-2-vinylpyridine(P) diblock copolymers, SP star-shaped block copolymers, PSP triblock copolymers, styrene(S)-isoprene(I) multiblock copolymers of the (SI)_n type, ISP triblock copolymers, SPP graft copolymers and their deuterated samples were prepared. Variations of the morphologies with compositions, molecular weight dependences of the lamellar domain sizes and conformations and distributions of block chains in the lamellar domains were studied in the strong segregation limit. Besides typical morphologies such as spherical, cylindrical and lamellar structures, ordered bi- and tri-continuous structures were found between cylindrical and lamellar structures for SP diblock copolymers, PSP and ISP triblock copolymers, respectively. The composition ranges of morphologies are different for the block and graft copolymers of different types. The molecular weight dependences of lamellar domain sizes are about the same, but their magnitudes are not always the same for the block and graft copolymers of different types. These results are well explained by the theories of Helfand-Wasserman and Semenov. Block chains in lamellae are extended along the direction perpendicular to lamellae, but they are contracted along the parallel direction. The former result is well explained by the theories, but the latter is not. Chains adjacent to the junction points between different block chains are localized near the domain interface, but chains at the free-ends of block chains are widely distributed in the domain with the maximum at the center of domain.     

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.     

Synthesis of high molecular weight comb block copolymers and their assembly into ordered morphologies in the solid state

This Article describes a simple two-step synthesis of comb block copolymers with molecular weights exceeding 1,000,000 g mol(-1) and their assembly into ordered morphologies in the solid state. This work is exciting because these polymers assembled into morphologies with domain sizes exceeding 100 nm and, in some examples, 200 nm without the use of additives. These materials reflected selected wavelengths of visible light, and these wavelengths could be affected by swelling with methylene chloride vapor. A comparison between the structures of comb block copolymers and linear block copolymers is presented with a discussion of important parameters affecting their assembly in the solid state. This Article will first describe the synthesis of comb block copolymers using ring opening metathesis polymerization and atom transfer radical polymerization and their subsequent characterization. The comb block copolymers, backbone polymers, and polystyrene arms were all characterized independent of each other and had low polydispersities. The comb block copolymers were assembled by dissolving in methylene chloride and allowing the solvent to evaporate. After thermal annealing, the polymers were characterized by scanning electron and optical microscopy. These polymers assembled into spherical, lamellar, and cylindrical arrays with domain sizes from 132 to 258 nm. This work extends the molecular architectures of polymers that can be assembled in the solid state, the molecular weights of block copolymers that were assembled, and the domain sizes that can be realized without the use of additives.     

Polybenzimidazole‐based block copolymers: From monomers to membrane electrode assemblies for high temperature polymer electrolyte membrane fuel cells

In this study, PBI‐based block copolymers were developed and their performance as membranes in high temperature polymer electrolyte membrane fuel cells was evaluated. This type of block copolymer consists of “phosphophilic” PBI and “phosphophobic” non‐PBI segments. The final properties of such block copolymers strongly depended on the length of the individual blocks and their chemical structures. In a systematic approach, a series of various block copolymers was synthesized and characterized both in terms of ex situ properties (e.g., proton conductivity, phosphoric acid uptake, swelling behavior) and in situ fuel cell tests. A very poor membrane‐electrode interface limited the performance of the membrane electrode assemblies, but was remarkably improved in power output, stability, and long‐term durability by treating the electrode interface with a fluorinated PBI derivative. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1831–1843     

Nano-scale structure change of amphiphilic di-block copolymer by blend

The phase transition and nano-scale ordered structure of four types of blends prepared from four di-block copolymers, consisting of hydrophilic poly(ethylenoxide) and hydrophobic poly(methacrylate) derivative, PEO_m-b-PMA(Az)_n having different PEO molecular length and same degree of polymerization of PMA(Az) were investigated. All blend systems formed hexagonal packed PEO cylinder structure, which was same with the nano-scale structure of these parent block copolymers. The SAXS and AFM observation suggested that the size of hexagonal structure of blend was larger than the average size of parent block copolymers. The melting enthalpy of PEO in blends was larger than the average value of parent block copolymers. DSC, SAXS and AFM observations indicated the miscible blend systems.     

环境响应性嵌段共聚物的合成、自组装及应用研究进展

近年来具有环境响应性的嵌段共聚物的研发受到了人们的广泛关注。该类型共聚物可以对外界环境刺激产生相应的结构、物理及化学性能的变化。根据外界环境刺激响应机理及类型的不同,可将其分为单一因素、双重因素以及三重因素刺激响应性嵌段共聚物三大类。针对每一类体系,本文重点综述了嵌段共聚物的设计合成、自组装以及应用等研究现状,并概括总结了各种有序聚集体(如胶束、囊泡等)随外界环境刺激(如pH、温度、光、CO_2、氧化还原剂等)所作出的响应性变化。最后,对智能型嵌段共聚物在药物控释、纳米容器制备、生物功能材料等方面潜在的应用价值和今后可能的发展方向进行了展望。     

Self-organization process of ordered structures in linear and star poly(styrene)-poly(isoprene) block copolymers: Gaussian models and mesoscopic parameters of polymeric systems

Mesoscopic simulations of linear and 3-arm star poly(styrene)-poly(isoprene) block copolymers was performed using a representation of the polymeric molecular structures by means of Gaussian models. The systems were represented by a group of spherical beads connected by harmonic springs; each bead corresponds to a segment of the block chain. The quantitative estimation for the bead-bead interaction of each system was calculated using a Flory-Huggins modified thermodynamical model. The Gaussian models together with dissipative particle dynamics (DPD) were employed to explore the self-organization process of ordered structures in these polymeric systems. These mesoscopic simulations for linear and 3-arm star block copolymers predict microphase separation, order-disorder transition, and self-assembly of the ordered structures with specific morphologies such as body-centered-cubic (BCC), hexagonal packed cylinders (HPC), hexagonal perforated layers (HPL), alternating lamellar (LAM), and ordered bicontinuous double diamond (OBDD) phases. The agreement between our simulations and experimental results validate the Gaussian chain models and mesoscopic parameters used for these polymers and allow describing complex macromolecular structures of soft condensed matter with large molecular weight at the statistical segment level.     

Topological “interfacial” polymer chemistry: Dependency of polymer “shape” on surface morphology and stability of layer structures when heating organized molecular films of cyclic and linear block copolymers of n‐butyl acrylate‐ethylene oxide

The “topological polymer chemistry” of amphiphilic linear and cyclic block copolymers at an air/water interface was investigated. A cyclic copolymer and two linear copolymers (AB‐type diblock and ABA‐type triblock copolymers) synthesized from the same monomers were used in this study. Relatively stable monolayers of these three copolymers were observed to form at an air/water interface. Similar condensed‐phase temperature‐dependent behaviors were observed in surface pressure–area isotherms for these three monolayers. Molecular orientations at the air/water interface for the two linear block copolymers were similar to that of the cyclic block copolymer. Atomic force microscopic observations of transferred films for the three polymer types revealed the formation of monolayers with very similar morphologies at the mesoscopic scale at room temperature and constant compression speed. ABA‐type triblock linear copolymers adopted a fiber‐like surface morphology via two‐dimensional crystallization at low compression speeds. In contrast, the cyclic block copolymer formed a shapeless domain. Temperature‐controlled out‐of‐plane X‐ray diffraction (XRD) analysis of Langmuir–Blodgett (LB) films fabricated from both amphiphilic linear and cyclic block copolymers was performed to estimate the layer regularity at higher temperatures. Excellent heat‐resistant properties of organized molecular films created from the cyclic copolymer were confirmed. Both copolymer types showed clear diffraction peaks at room temperature, indicating the formation of highly ordered layer structures. However, the layer structures of the linear copolymers gradually disordered when heated. Conversely, the regularity of cyclic copolymer LB multilayers did not change with heating up to 50 °C. Higher‐order reflections (d₀₀₂, d₀₀₃) in the XRD patterns were also unchanged, indicative of a highly ordered structure. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 486–498     

Thermal Degradation and Electrical Properties of Random and Block Piperazine Copolyamides

The thermal degradation of random and block copolymers of terephthaloyl trans-2,5-dimethylpiperazine/isophthaloyl trans-2,5-dimethylpiperazine were investigated in terms of rates, activation energies, degradation products, and electrical properties. The rates of degradation and the nature of the volatile degradation products indicate that both random and block copolymers follow a nearly random free-radical type of cleavage in vacuum with activation energies between 59 and 61 kcal/mole. In the temperature range 390=440°C, the block copolymers are significantly more stable in a vacuum (the rates of degradation are two to four times slower) than the random copolymers. In contrast to the random copolymers, the block copolymers showed only slight frequency dependence of their dielectric constants and dissipation factors between 0.1 and 100 kcps.