Vertically Oriented Nanostructures of Poly(3-dodecylthiophene)-Containing Rod–Coil Block Copolymers

Lee, Kyu Seong; Lee, Jae Yong; Choi, Chungryong; Seo, Yeseong; Moon, Hong Chul; Kim, Jin Kon

doi:10.1021/acs.macromol.7b02739

Cited by 8 publications

(13 citation statements)

References 56 publications

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“…In this case, however, perpendicular lamellae and cylinders were only observed in film thicknesses below 2L 0 and 3L 0 , respectively (this brings up an alluring question: would the thickness window for perpendicular features be expanded if the inner block were to have a lower γ than the outer block, analogous to a star‐shaped version of an ABA triBCP?). Similar results were produced with rod–coil star BCPs with 18 polystyrene‐ block ‐poly(3‐dodecylthiophene) (PS‐ b ‐P3DDT) arms . Although P3DDT had a significantly lower γ than PS, perpendicular microdomains were observed for film thicknesses below 2L 0 .…”

Section: Architecture Effectsupporting

confidence: 70%

“…Of these reports, reports that promote perpendicular microdomains via thermal annealing are highly promising because they are easily reproducible and industry friendly. These methods include substrate modification, use of top coats, incorporation of additives, exploitation of the architecture effect, use of modified or newly synthesized BCPs, and use of cold zone annealing techniques . Recently, the introduction of top coats has paved exciting roads to thermally induced perpendicular Si‐containing microdomains that could only be attained via solvent vapor annealing in the past.…”

Section: Introductionmentioning

confidence: 99%

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Thermal Approaches to Perpendicular Block Copolymer Microdomains in Thin Films: A Review and Appraisal

Wang

Kim

Bang

2018

Macromol. Rapid Commun.

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Block copolymer thin films are highly versatile and accessible materials capable of producing nanofeatures in the size regime of a few to hundreds of nanometers by a simple spin‐coating‐and‐anneal process. Unfortunately, this simple protocol usually leads to parallel microdomains, which limits the applicability of such nanofeatures. A great deal of effort has been put into achieving perpendicular microdomains, but those that incorporate thermal annealing are arguably the most practical and reproducible in the lab and industry. This review discusses the recent ongoing efforts on various thermal approaches to achieving perpendicular microdomains in order to provide the readers with a toolbox to work with.

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Section: Architecture Effectsupporting

confidence: 70%

Section: Introductionmentioning

confidence: 99%

Thermal Approaches to Perpendicular Block Copolymer Microdomains in Thin Films: A Review and Appraisal

Wang

Kim

Bang

2018

Macromol. Rapid Commun.

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“…However, rigid rods are not a perfect analogy for this behavior, because they are known to interdigitate rather than pack end−end, which would result in half the observed periodicity. 61 In order to pack end−end, there must be some rearrangement in the side chains in order to maintain a uniform interfacial area per junction between the two components in the lamellar morphology. In this molecule, the radius of the PS side chains is greater than that of the PLA side chains, and in the bulk, this differential between the side chain volumes can be remedied by changes in the backbone conformation.…”

Section: Resultsmentioning

confidence: 99%

“…This suggests that as the BBCP is increasingly confined, l p increases, up until the point where the entire chain is extended like a rigid rod. However, rigid rods are not a perfect analogy for this behavior, because they are known to interdigitate rather than pack end–end, which would result in half the observed periodicity . In order to pack end–end, there must be some rearrangement in the side chains in order to maintain a uniform interfacial area per junction between the two components in the lamellar morphology.…”

Section: Resultsmentioning

confidence: 99%

Confinement and Processing Can Alter the Morphology and Periodicity of Bottlebrush Block Copolymers in Thin Films

et al. 2020

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Bottlebrush block copolymers (BBCPs) are intriguing architectural variations on linear BCPs with highly tunable structure. Confinement can have a significant impact on polymer assembly, giving rise to changes in morphology, assembly kinetics, and properties like the glass transition. Given that confinement leads to significant changes in the persistence length of bottlebrush homopolymers, it is reasonable to expect that BBCPs will see significant changes in their structure and periodicity relative to the bulk morphology. Understanding how confinement influences assembly will be important for designing BBCPs for thin film applications including membranes, integrated photonic structures, and potentially BCP lithography. In order to study the effects of confinement on BBCP conformation and morphology, a blade coating was used to prepare films with continuous variation in film thickness. Unlike thin films of linear BCPs, islands/holes were not observed, and instead mixtures of parallel and perpendicular morphologies emerge after annealing. The lamellar periodicity (L 0 ) of the morphologies is found to be thickness dependent, increasing L 0 with decreasing film thickness for blade coated films. Films coated out of tetrahydrofuran (THF) resulted in a single well-defined lamellar periodicity, verified through atomic force microscopy (AFM) and grazing incidence small-angle X-ray scattering (GISAXS), which increases dramatically from the bulk value (30.6 nm) and continues to increase as the film thickness decreases. The largest observed L 0 was 65.5 nm, and this closely approaches the estimated upper limit of 67 nm corresponding to a fully extended backbone in a bilayer arrangement. Films coated out of propylene glycol methyl ether acetate (PGMEA) resulted in a mixture of perpendicular lamellae and a smaller, likely cylindrical morphology. The lamellar portion of the film shows the same thickness dependence as the lamellae observed in the THF coated films. The scaling of the lamellar L 0 with respect to film thickness follows predictions for confined semiflexible polymers with weak excluded volume interactions and can be related to models for confinement of DNA. Spin coated films shows the same reduction in periodicity, although at very different film thicknesses. This result suggests that the material has shallow free-energy barriers to transitioning between different L 0 and morphologies, a property that could be taken advantage of for patterning diverse structures with a single material.

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“…Also, the thin-film morphology of star-shaped BCPs exhibited a different behavior from linear BCPs. − Some research groups reported that vertically oriented cylindrical and lamellar microdomains of star-shaped BCPs were formed without pre- or post-treatment. − , Kim and co-workers showed that cylindrical and lamellar microdomains of [(PMMA- b -PS) 18 ] were vertically oriented on diverse substrates . Also, Ho and co-workers reported that the vertical orientation of lamellae of three- and four-arm star-shaped PS -b -poly(dimethylsiloxane) [(PS- b -PDMS) n ( n = 3, 4)] were formed by controlling the surface tension of the top film side by oxygen plasma treatment .…”

Section: Introductionmentioning

confidence: 99%

Thin-Film Morphology of Symmetric Six-Arm Star-Shaped Poly(methyl methacrylate)-block-Polystyrene Copolymers

et al. 2020

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We investigated, via atomic force microscopy and fieldemission scanning electron microscopy, the thin-film morphology of six-arm star-shaped poly(methyl methacrylate)-b-polystyrene [(PMMA-b-PS) 6 ] with the volume fraction of PS block of ∼0.5. At smaller molecular weight (M) but higher than the critical molecular weight (M crit ) above which block copolymers start to microphase-separate, the thin-film morphology greatly depends on the surface tension at the air side when a substrate has preferential interaction with one block (PMMA). For a near-neutral air surface, interesting tube-like nanostructures, instead of vertically oriented lamellae, were formed at the top of the film, while a PMMA layer was formed on the bottom film, contacting the silicon substrate with a native oxide. This is because the combination of vertical and parallel lamellae generates a huge energy penalty at the T-junction connecting these two different lamellar orientations. Tube-like nanostructures were also formed on other substrates that are preferential to one block, for instance, gold or a substrate grafted by a PS brush, when the film thickness does not meet the commensurability. On the other hand, when M is much higher than M crit , vertical lamellae were formed throughout the entire film thickness. The self-consistent field theory supported the experimental findings.

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Vertically Oriented Nanostructures of Poly(3-dodecylthiophene)-Containing Rod–Coil Block Copolymers

Cited by 8 publications

References 56 publications

Thermal Approaches to Perpendicular Block Copolymer Microdomains in Thin Films: A Review and Appraisal

Thermal Approaches to Perpendicular Block Copolymer Microdomains in Thin Films: A Review and Appraisal

Confinement and Processing Can Alter the Morphology and Periodicity of Bottlebrush Block Copolymers in Thin Films

Thin-Film Morphology of Symmetric Six-Arm Star-Shaped Poly(methyl methacrylate)-block-Polystyrene Copolymers

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