Strain‐Induced Phase Morphology in Melt Drawn Ultrathin Highly Oriented Block Copolymer Films

Keller, Thomas F.; Semmler, Christian

doi:10.1002/marc.200800060

Cited by 8 publications

(4 citation statements)

References 44 publications

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“…The confinement of polymer in thin films provides scientists with an extraordinary opportunity to study how their physical properties may be altered in comparison to the ones of their bulk counterparts. This is a very important issue as polymer thin films have many applications in biomedical, 1 packaging, 2 and flexible photovoltaic 3 industries, just to cite a few. Although industrial processes using polymer in thin films are well controlled, the effects of confinement remain intensively debated.…”

Section: ■ Introductionmentioning

confidence: 99%

Densification and Depression in Glass Transition Temperature in Polystyrene Thin Films

et al. 2014

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Ellipsometry and X-ray reflectivity were used to characterize the mass density and the glass transition temperature of supported polystyrene (PS) thin films as a function of their thickness. By measuring the critical wave vector (qc) on the plateau of total external reflection, we evidence that PS films get denser in a confined state when the film thickness is below 50 nm. Refractive indices (n) and electron density profiles measurements confirm this statement. The density of a 6 nm (0.4 gyration radius, Rg) thick film is 30% greater than that of a 150 nm (10Rg) film. A depression of 25 °C in glass transition temperature (Tg) was revealed as the film thickness is reduced. In the context of the free volume theory, this result seems to be in apparent contradiction with the fact that thinner films are denser. However, as the thermal expansion of thinner films is found to be greater than the one of thicker films, the increase in free volume is larger for thin films when temperature is raised. Therefore, the free volume reaches a critical value at a lower Tg for thinner films. This critical value corresponds to the onset of large cooperative movements of polymer chains. The link between the densification of ultrathin films and the drop in their Tg is thus reconciled. We finally show that at their respective Tg(h) all films exhibit a critical mass density of about 1.05 g/cm(3) whatever their thickness. The thickness dependent thermal expansion related to the free volume is consequently a key factor to understand the drop in the Tg of ultrathin films.

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Section: ■ Introductionmentioning

confidence: 99%

Densification and Depression in Glass Transition Temperature in Polystyrene Thin Films

et al. 2014

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“…19 During the MD process, a highly oriented and nanostructured surface develops on the MD UHMWPE films by strain-induced, crystallization-driven self-assembly. [20][21][22][23] The surface morphology of MD UHMWPE films consists of highly regular, stacked nanocrystalline lamellae of high orientation that are interconnected by amorphous interlayers. 19 For the protein adsorption in the present work, human plasma fibrinogen (HPF) was chosen, as it is intrinsically anisotropic, amphiphilic, and relevant for current applications of UHMWPE and further polymeric implant materials, such as polyethylene terephthalate (PET) 24 or poly-(lactide)-based homo-or copolymers.…”

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confidence: 99%

“…Previously, we reported the first time creation of ultraflat, highly oriented UHMWPE films by a melt drawing (MD) technique . During the MD process, a highly oriented and nanostructured surface develops on the MD UHMWPE films by strain-induced, crystallization-driven self-assembly. − The surface morphology of MD UHMWPE films consists of highly regular, stacked nanocrystalline lamellae of high orientation that are interconnected by amorphous interlayers …”

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confidence: 99%

How the Surface Nanostructure of Polyethylene Affects Protein Assembly and Orientation

et al. 2011

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Protein adsorption plays a key role in the biological response to implants. We report how nanoscale topography, chemistry, crystallinity, and molecular chain anisotropy of ultrahigh molecular weight polyethylene (UHMWPE) surfaces affect the protein assembly and induce lateral orientational order. We applied ultraflat, melt drawn UHMWPE films to show that highly oriented nanocrystalline lamellae influence the conformation and aggregation into network structures of human plasma fibrinogen by atomic force microscopy with unprecedented clarity and molecular resolution. We observed a transition from random protein orientation at low concentrations to an assembly guided by the UHMWPE surface nanotopography at a close to full surface coverage on hydrophobic melt drawn UHMWPE. This assembly differs from the arrangement at a hydrophobic, on the nanoscale smooth UHMWPE reference. On plasma-modified, hydrophilic melt drawn UHMWPE surfaces that retained their original nanotopography, the influence of the nanoscale surface pattern on the protein adsorption is lost. A model based on protein-surface and protein-protein interactions is proposed. We suggest these nanostructured polymer films to be versatile model surfaces to provide unique information on protein interactions with nanoscale building blocks of implants, such as nanocrystalline UHMWPE lamellae. The current study contributes to the understanding of molecular processes at polymer biointerfaces and may support their future design and molecular scale tailoring.

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“…Recently, flow-induced approaches such as casting and droplet pinning have been demonstrated to control the orientation of microdomains of a block copolymer film. Flow provides a simple and efficient way to achieve alignment, requiring only straightforward restrictions. − Russell and co-workers used a droplet pinning approach to successfully fabricate domains of highly oriented cylinders in the course of solvent evaporation. They proposed that the alignment and the degree of orientation of nanoscopic cylinders were guided by the evaporation-induced flow field at the three-phase contact line.…”

Section: Introductionmentioning

confidence: 99%

Dewetting-Induced Alignment and Ordering of Cylindrical Mesophases in Thin Block Copolymer Films

Zhang

Wang

et al. 2020

Macromolecules

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The fabrication of ordered self-assembled nanopatterns in block copolymer films, especially aligned nanostructures, has gained considerable attention. Here, we present a simple approach based on dewetting-induced alignment of cylindrical mesophases in thin polystyreneblock-poly(2-vinylpyridine) (PS-b-P2VP) films. In the course of dewetting enabled by solvent vapor annealing, cylinders aligned parallel to the dewetting contact line with the size of the ordered domain increasing in the direction normal to the dewetting front. The alignment of cylindrical mesophases was driven by the dewetting flow field and by minimization of the elastic energy of the P2VP cylinders in a confined space. We observed a power-law increase of the orientation parameter (f) for the P2VP cylinders with increasing time (t) of hole growth: f ∼ t 1/3 . Arrays of precisely aligned cylinders were achieved in long filaments generated by the coalescence of adjacent dewetting holes.

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Strain‐Induced Phase Morphology in Melt Drawn Ultrathin Highly Oriented Block Copolymer Films

Cited by 8 publications

References 44 publications

Densification and Depression in Glass Transition Temperature in Polystyrene Thin Films

Densification and Depression in Glass Transition Temperature in Polystyrene Thin Films

How the Surface Nanostructure of Polyethylene Affects Protein Assembly and Orientation

Dewetting-Induced Alignment and Ordering of Cylindrical Mesophases in Thin Block Copolymer Films

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