Templated Self‐Assembly of Block Copolymers: Top‐Down Helps Bottom‐Up

Cheng, Joy Y.; Ross, Caroline A.; Smith, Henry I.; Thomas, Edwin L.

doi:10.1002/adma.200502651

Cited by 686 publications

(644 citation statements)

References 134 publications

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“…Unlike carbon nanotubes that are produced by synthetic, bottom-up methods, electrospun nanofibers are produced through a topdown nano-manufacturing process, which results in low-cost electrospun nanofibers that are also relatively easy to align, assemble and process into applications. 22 Therefore, electrospinning and the resulting nanofibers are of great scientific, military and commercial interests, and have been widely investigated in the past decade. [23][24][25][26][27][28][29][30] In electrospinning, a spin dope (e.g., a polymer solution with a viscosity similar to that of honey) is placed in a container (e.g., a regular glass pipette), and a high DC voltage, usually in the range from 5 to 40 kV, is applied to the solution through an electrode (e.g., a copper wire).…”

Section: Introductionmentioning

confidence: 99%

Crystalline Morphology and Polymorphic Phase Transitions in Electrospun Nylon-6 Nanofibers

et al. 2007

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Uniform nylon 6 nanofibers with diameters around 200 nm were prepared by electrospinning. Polymorphic phase transitions and crystal orientation of nylon 6 in unconfined (i.e., as-electrospun) and a high T g (340 °C) polyimide confined nanofibers were studied. Similar to melt-spun nylon 6 fibers, electrospun nylon 6 nanofibers also exhibited predominant, meta-stable γ crystalline form, and the γ-crystal (chain) axes preferentially oriented parallel to the fiber axis. Upon annealing above 150 °C, γ-form crystals gradually melted and recrystallized into the thermodynamically stable α-form crystals, which ultimately melted at 220 °C. Release of surface tension accompanied this meltrecrystallization process, as revealed by differential scanning calorimetry. For confined nanofibers, both the melt-recrystallization and surface tension release processes were substantially depressed; γ-form crystals did not melt and recrystallize into α-form crystals until 210 °C, only 10 °C below the T m at 220 °C. After complete melting of nano-confined crystals at 240 °C and recrystallization at 100 °C, only α-form crystals oriented perpendicular to the nanofiber axis were obtained. In the polyimide-confined nanofibers, the Brill transition (from the monoclinic α-form to a high temperature monoclinic form) was observed at 180-190 °C, which was at least 20 °C higher than that in unconfined nylon 6 at approximately 160 °C. This, again, was attributed to the confinement effect.

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Section: Introductionmentioning

confidence: 99%

Crystalline Morphology and Polymorphic Phase Transitions in Electrospun Nylon-6 Nanofibers

et al. 2007

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“…Block copolymer self-assembly is a simple, cost-effective, and scalable maskless nanofabrication technique, in which the feature sizes and geometries can be controlled via the chain length and volume fractions of the blocks. [22][23][24] Previously, we have described the self-assembly of a poly(styrene-bdimethylsiloxane) (PS-PDMS) diblock copolymer, which forms extraordinarily well-ordered structures due to its large Flory-Huggins interaction parameter. [25][26][27] The structures have an excellent etch-selectivity between the two polymer blocks as a result of the high Si content in the PDMS block, [25][26][27] and this facilitates pattern transfer into an underlying functional material.…”

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confidence: 99%

Nanowire Conductive Polymer Gas Sensor Patterned Using Self-Assembled Block Copolymer Lithography

et al. 2008

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Nanostructured conjugated organic thin films are essential building blocks for highly integrated organic devices. We demonstrate the largearea fabrication of an array of well-ordered 15 nm wide conducting polymer nanowires by using an etch mask consisting of self-assembled patterns of cylinder-forming poly(styrene-b-dimethylsiloxane) diblock copolymer confined in topographic templates. The poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) nanowires operated as an ethanol vapor sensor, suggesting that the electronic properties of the organic film were preserved during the patterning processes. The higher sensitivity to ethanol vapor, compared to an unpatterned film with the same thickness, was attributed to the enhanced surface-to-volume ratio of the nanowire array.A molecular rectifier, theoretically proposed by Ratner and Aviram in 1974, was the starting point for a boom in molecular electronics research that has persisted for the last three decades. 1 Later, single-molecule field-effect transistors and logic gates were also conceptually proposed, 2 and Reed et al. first reported single-molecule conductance measurements through benzene-1,4-dithiol. 3 The development of conductive polymers has continued to attract interest for many different applications including optoelectronic devices, 4-6 field effect transistors, 7,8 and chemical or biological sensors. 8,9 In these applications, device performance has been improved by miniaturizing the feature sizes down to the nanoscale regime, 10,11 and there is considerable interest in methods that enable the patterning of electronically active polymers on the nanoscale.Various fabrication techniques have been developed for generating conducting polymer nanowires. Chemical or electrochemical growth without templates usually produces entangled nanowires with a large distribution in diameter and length, which is undesirable in terms of performance and reproducibility, despite the convenience of fabrication. 12-17 For better-organized structures, scanning-probe and electronbeam patterning have been employed to direct the growth of conducting polymer nanowires. 11,18,19 Recently, spontaneous ordering of polymer nanowires was induced within a submicron gap between electrodes fabricated using a focused ion beam. 20 However, the throughput and manufacturability of these methods are limited by the serial nature of the patterning techniques. Well-ordered conducting polymer nanopatterns have also been produced by nanoimprint lithography, 21 but this technique requires fabrication of master molds.In this communication, we report fabrication of well-ordered arrays of 15 nm wide, 35 nm period poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) conducting polymer nanowires, made over areas of several square centimeters using a self-assembled block copolymer mask, and we demonstrate the capability of the patterned structures to act as an ethanol vapor sensor, confirming the preservation of the electronic properties of the PEDOT:PSS during patterning. Bloc...

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“…As it has been shown in this study, on SiO 2 at pH 4, there was a thin sophorolipids layer, and the SEM images show a network similar to the one observed in the surface assembly of block copolymers. 20,103 By definition, the spinodal decomposition was a clustering phase change from a homogeneous matter that separated spontaneously into two phases due to a small fluctuation of density or composition. 104 Two other phenomena could explain the phase separation within a film.…”

Section: Q8mentioning

confidence: 99%

Surface-induced assembly of sophorolipids

Peyre

Hamraoui

Faustini

et al. 2017

Phys. Chem. Chem. Phys.

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The surface self-assembly properties of acidic sophorolipids, a bolaform microbial glycolipids with pHresponsive properties in solution, were studied based on the chemical nature of the support and pH of the solution. Sophorolipids generally form micelles in water but formation of morphologies like platelets and twisted fibers depending on pH have also been reported. The surface self-assembly was achieved using dip-coating on three different substrates namely gold, silicon(111) and TiO 2 anatase. Deposition conditions (dip-coating withdrawal speed, relative humidity, temperature) were tested, and it was found that optimum self-assembly occurred at a withdrawal speed of 1 mm s À1 , T of 25 1C and relative humidity of 25%. The local structure of the sophorolipid films was characterized by Atomic Force Microscopy, while Scanning Electron Microscopy was used to characterize the spatial homogeneity. We also attempted to correlate dispersive, electron donor and electron attractor surface energy components, using Good-Van Oss's approach, and the behavior of sophorolipids. We found that when the surface energy is dominated by dispersive components, sophorolipids spontaneously assemble into entangled needles at all pH values (4, 6 and 11). However, when the surface energy is dominated by electronic components, pH has a strong influence on the surface self-assembly. We could discriminate three major organizations: homogeneous layer, isolated aggregates and a two-dimensional network similar to block copolymer surface self-assembly.

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Templated Self‐Assembly of Block Copolymers: Top‐Down Helps Bottom‐Up

Cited by 686 publications

References 134 publications

Crystalline Morphology and Polymorphic Phase Transitions in Electrospun Nylon-6 Nanofibers

Crystalline Morphology and Polymorphic Phase Transitions in Electrospun Nylon-6 Nanofibers

Nanowire Conductive Polymer Gas Sensor Patterned Using Self-Assembled Block Copolymer Lithography

Surface-induced assembly of sophorolipids

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