Surface Reorganization of an Amphiphilic Block Copolymer Film Studied by NEXAFS Spectroscopy

Théato, Patrick; Brehmer, Martin; Conrad, Lars S.; Frank, Curtis W.; Funk, Lutz; Yoon, Do Y.; Lüning, J.

doi:10.1021/ma0509964

Cited by 13 publications

(25 citation statements)

References 25 publications

(33 reference statements)

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“…Previously, we have employed X-ray absorption spectroscopy to investigate the chemical composition of the surface of thin films of the block copolymer PS-b-PAEES and its evolution upon equilibration in a wet or dry environment. 28 Similar work has been done for a copolymer with PEGylated and fluoroalkyl side chains. 35 We showed that alternating equilibration leads to a reproducible, essentially complete exchange of the molecular blocks composing the surface layer of the film; from hydrophilic PAEES blocks after water equilibration to hydrophobic PS blocks after vacuum equilibration and vice versa.…”

Section: Full Papermentioning

confidence: 86%

“…For example, Senshu et al investigated the structural ordering under wet and dry conditions of poly(2‐hydroxyethyl)methacrylate‐ block ‐polyisoprene and poly(2‐hydroxyethyl)methacrylate‐ block ‐polystyrene interfaces by contact angle and transmission electron microscopy measurements. Morphology and chemical composition of the surface of thin amphiphilic diblock copolymer films have also been intensively studied in the past. Less is known, however, about the interplay between bulk order and surface properties and their respective influence on each other.…”

Section: Introductionmentioning

confidence: 99%

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Surface and bulk ordering in thin films of a symmetrical diblock copolymer

Vodungbo

Nilles

et al. 2013

J Polym Sci B Polym Phys

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Amphiphilic diblock copolymers have the ability to adapt their surface's molecular composition to the hydrophilicity of their environment. In the case of about equal volume fractions of the two polymer blocks, the bulk of these polymers is known to develop a laminar ordering. We report here our investigation of the relationship between bulk ordering and surface morphology/chemical composition in thin films of such an amphiphilic diblock copolymer. Upon annealing in vacuum, the expected lamella ordering in the bulk of the film is observed and we find the morphology of the film surface to be defined by the thickness of the as-deposited film: If the asdeposited thickness matches the height of a lamella stack, then the film exhibits a smooth surface. Otherwise, an incomplete lamella forms at the film surface. We show that the coverage of this incomplete layer can be quantified by X-ray reflectivity. To establish the lamella ordering in the bulk, the film needs to be annealed above the glass temperature of the two blocks. Molecular segregation at the film surface, however, is already occurring at temperatures well below the glass temperature of the two blocks. This indicates that below the glass temperature of the blocks the bulk of the thin film is "frozen," whereas the polymer chains composing the surface lamella have an increased mobility.

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Section: Full Papermentioning

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Surface and bulk ordering in thin films of a symmetrical diblock copolymer

Vodungbo

Nilles

et al. 2013

J Polym Sci B Polym Phys

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“…NEXAFS measurements allowed it to detect the surface reconstruction associated with this perturbation by detecting the functional groups exposed at the surface. [10] The block copolymers originally investigated for this purpose [9] had rather high T g -values. Thus, a solvent was necessary to reduce the T g of the hydrophilic block composed of hydroxystyrene by swelling.…”

Section: Full Papermentioning

confidence: 99%

“…We could also show the change in the chemical composition of the surface during the reconstruction process of a thin film of P4-block-P3 by surface-sensitive NEXAFS spectroscopy. [10] An example of such a surface reconstruction process in contact with water is shown for a thin film of P1-block-P4-2 in Figure 3. In this case a thin film (about 150 nm) of the block copolymer was spin-coated on a silicon wafer.…”

Section: General Partmentioning

confidence: 99%

Novel Amphiphilic Styrene‐Based Block Copolymers for Induced Surface Reconstruction

Funk

Brehmer

Zentel

et al. 2007

Macro Chemistry & Physics

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This paper describes the synthesis of amphiphilic block copolymers by living radical polymerization (NMP) of new styrene‐like monomers. The polar monomers (ethylene oxide side chains and free hydroxyl‐ or amino‐groups after deprotection) were polymerized in a “protected form” to adjust the solubility of the monomers. In this way high molar mass polymers with a narrow polydispersity (around or below 1.2) were accessible. In the bulk state hydrophobic and hydrophilic domains demix. By exposing thin films of these polymers to vacuum (air) or alternatively to water or a hydrophilic surface it becomes possible to switch the surface polarity reversibly between contact angles of about 105° and 83° as a result of surface reconstruction. Through side chains of different length and with different functionalities, it was possible to adjust the glass transition temperatures to values between −2 °C to 140 °C for the hydrophilic blocks and −30 °C to 100 °C for the hydrophobic block. The wide range of the glass temperatures allowed it to find a block copolymer system with a slow kinetic concerning the surface reconstruction process, so that a mechanistic examination of the process by AFM was possible. It got, thereby, possible to detect the break‐up of the hydrophobic surface lamella and the upfold of the hydrophilic lamella in contact with water.magnified image

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“…However, no direct information regarding surface chemical composition is obtained by these techniques. Some groups currently use the near‐edge X‐ray absorption fine structure spectroscopy technique (NEXAFS) to investigate surface reconstruction of prehydrated surfaces in vacuum environment 10–12. This technique is very surface‐sensitive but requires access to a synchrotron light source.…”

Section: Introductionmentioning

confidence: 99%

Optimization of cryo‐XPS analyses for the study of thin films of a block copolymer (PS‐PEO)

Delcroix¹,

Zuyderhoff²,

Genet³

et al. 2011

Surface & Interface Analysis

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The water-induced surface reorganization of a thin film of a block copolymer [polystyrene-b-poly(ethylene oxide), PS-PEO], was studied by cryogenic X-ray photoelectron spectroscopy (cryo-XPS). Experimental parameters were examined with a view to optimize the analysis. The absence of artifacts due to the low temperature of analysis was checked, and the influence of the procedure used for sample hydration before analysis was investigated. Adequate timing of the different steps of the analysis and temperature program was also established. With this optimized protocol, an important reorganization of the block copolymer was detected, showing more pronounced exposure of the PEO block at the outermost surface in hydrated compared to dry environment. As this type of polymer surface is prone to be used for biomedical applications, an accurate knowledge of the chemical composition of the outermost surface in aqueous environments is crucial. The development of this technique is therefore promising for related systems.

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Surface Reorganization of an Amphiphilic Block Copolymer Film Studied by NEXAFS Spectroscopy

Cited by 13 publications

References 25 publications

Surface and bulk ordering in thin films of a symmetrical diblock copolymer

Surface and bulk ordering in thin films of a symmetrical diblock copolymer

Novel Amphiphilic Styrene‐Based Block Copolymers for Induced Surface Reconstruction

Optimization of cryo‐XPS analyses for the study of thin films of a block copolymer (PS‐PEO)

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