A Transition from Cylindrical to Spherical Morphology in Diblock Copolymer Thin Films

Niihara, Ken Ichi; Sugimori, Hidekazu; Matsuwaki, Ukyo; Hirato, Fumio; Morita, Hiroshi; Doi, Masao; Masunaga, Hiroyasu; Sasaki, Sono; Jinnai, Hiroshi

doi:10.1021/ma801892p

Cited by 32 publications

(22 citation statements)

References 54 publications

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“…For example, not only the orientation of cylindrical structures but also morphologies change with different film thicknesses. 39 Note that perforated lamellar structures have been induced by the confinement effect. 38 …”

Section: Morphologies Of Bcp Under Confinementmentioning

confidence: 99%

Three-Dimensional Visualization and Characterization of Polymeric Self-Assemblies by Transmission Electron Microtomography

et al. 2017

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* S Supporting Information CONSPECTUS: Self-assembling structures and their dynamical processes in polymeric systems have been investigated using three-dimensional transmission electron microscopy (3D-TEM). Block copolymers (BCPs) self-assemble into nanoscale periodic structures called microphase-separated structures, a deep understanding of which is important for creating nanomaterials with superior physical properties, such as high-performance membranes with well-defined pore size and high-density data storage media. Because microphase-separated structures have become increasingly complicated with advances in precision polymerization, characterizing these complex morphologies is becoming increasingly difficult. Thus, microscopes capable of obtaining 3D images are required. In this article, we demonstrate that 3D-TEM is an essential tool for studying BCP nanostructures, especially those self-assembled during dynamical processes and under confined conditions. The first example is a dynamical process called order−order transitions (OOTs). Upon changing temperature or pressure or applying an external field, such as a shear flow or electric field, BCP nanostructures transform from one type of structure to another. The OOTs are examined by freezing the specimens in the middle of the OOT and then observing the boundary structures between the preexisting and newly formed nanostructures in three-dimensions. In an OOT between the bicontinuous double gyroid and hexagonally packed cylindrical structures, two different types of epitaxial phase transition paths are found. Interestingly, the paths depend on the direction of the OOT. The second example is BCP self-assemblies under confinement that have been examined by 3D-TEM. A variety of intriguing and very complicated 3D morphologies can be formed even from the BCPs that self-assemble into simple nanostructures, such as lamellar and cylindrical structures in the bulk (in free space). Although 3D-TEM is becoming more frequently used for detailed morphological investigations, it is generally used to study static nanostructures. Although OOTs are dynamical processes, the actual experiment is done in the static state, through a detailed morphological study of a snapshot taken during the OOT. Developing time-dependent nanoscale 3D imaging has become a hot topic. Here, the two main problems preventing the development of in situ electron tomography for polymer materials are addressed. First, the staining protocol often used to enhance contrast for electrons is replaced by a new contrast enhancement based on chemical differences between polymers. In this case, no staining is necessary. Second, a new 3D reconstruction algorithm allows us to obtain a high-contrast, quantitative 3D image from fewer projections than is required for the conventional algorithm to achieve similar contrast, reducing the number of projections and thus the electron beam dose. Combining these two new developments is expected to open new doors to 3D in situ real-time structural observation of polymer materials.

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Section: Morphologies Of Bcp Under Confinementmentioning

confidence: 99%

Three-Dimensional Visualization and Characterization of Polymeric Self-Assemblies by Transmission Electron Microtomography

et al. 2017

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“…A thin film is defined as a one-dimensional (1D) confinement system, in which the boundary condition is determined by film thickness. 23,26,[29][30][31][32][33][34] In a thin film of an asymmetric block copolymer that naturally forms cylindrical structures, cylinders align parallel and perpendicular to the substrate, and perforated lamellae are formed depending on film thickness. 23 In contrast, cylindrical pores such as those in an anodized alumina membrane offer two-dimensional (2D) confinement because they have two boundary conditions.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional observation of confined phase-separated structures in block copolymer nanoparticles

et al. 2012

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The effect of confinement on microphase-separated structures of a diblock copolymer is investigated in nanoparticles serving as a three-dimensional (3D) confinement system. We succeeded in preparing nanoparticles having various types of complex structures from hydrophobic diblock copolymers by a simple solvent evaporation method. The detailed 3D structural analysis of the nanoparticles by transmission electron microtomography (TEMT) revealed that complex structures were found only to form in the nanoparticle surface region, the thickness of which corresponded to the single-molecule length of the block copolymer in the bulk state. These results indicate that 3D confinement fundamentally affects block copolymer self-assemblies most strongly in the surface region of nanoparticles but only weakly in the central region.

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“…The frustrated phases receive much attention in both theoretical and experimental science communities. Various types of confinement spaces have been used, including one‐dimensional confinement, 1D (thin films), two‐dimensional, 2D (e.g., cylindrical pores of anodized aluminum oxide membranes), and three‐dimensional, 3D (e.g., spherical pores of inverse colloid crystals) confinements. Morphologies in a confinement are mainly governed by three parameters: (i) the size of the confinement, (ii) its shape, and (iii) the interfacial energy between the polymer and outer matrix.…”

Section: Introductionmentioning

confidence: 99%

Multipod structures of lamellae‐forming diblock copolymers in three‐dimensional confinement spaces: Experimental observation and computer simulation

Higuchi

Pinna

Zvelindovsky

et al. 2016

J Polym Sci B Polym Phys

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The three-dimensional (3D) confinement effect on the microphase-separated structure of a diblock copolymer was investigated both experimentally and computationally. Block copolymer nanoparticles were prepared by adding a poor solvent into a block copolymer solution and subsequently evaporating the good solvent. The 3D structures of the nanoparticles were quantitatively determined with transmission electron microtomography (TEMT). TEMT observations revealed that various complex structures, including tennis-ball, mushroom-like, and multipod structures, were formed in the 3D confinement. Detailed structural analysis, showed that one block of the diblock copolymer slightly prefers to segregate into the particle surface compared with the other block. The observed structures were further elaborated using cell dynamics computer simulation. V C 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 00, 000-000 KEYWORDS: 3D confinement; block copolymers; cell dynamic simulation; electron microscopy; electron tomography; microphaseseparated structure; phase separation; simulations INTRODUCTION Block copolymers consist of covalently bonded dissimilar polymer segments and can spontaneously form periodic microphase-separated structures. The characteristic lengths of the structures depend on their molecular weights and are generally in the range from 10 to 100 nm. The typical morphologies of diblock copolymers include spheres, cylinders, gyroids, and lamellae, depending on their volume fraction. Highly ordered nanostructures can be prepared by simple coating techniques, thus microphase-separated structures have been developed for diverse applications, for example, etching masks in lithography, 1 photonic crystals, 2 filtration, 3 and photovoltaic devices. 4 The performance of these applications is governed by the morphologies of the microphase-separated structures, 5 so control of morphologies and exploration of novel structures are challenging.

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A Transition from Cylindrical to Spherical Morphology in Diblock Copolymer Thin Films

Cited by 32 publications

References 54 publications

Three-Dimensional Visualization and Characterization of Polymeric Self-Assemblies by Transmission Electron Microtomography

Three-Dimensional Visualization and Characterization of Polymeric Self-Assemblies by Transmission Electron Microtomography

Three-dimensional observation of confined phase-separated structures in block copolymer nanoparticles

Multipod structures of lamellae‐forming diblock copolymers in three‐dimensional confinement spaces: Experimental observation and computer simulation

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