5 research outputs found

    Distortion of a Unit Cell versus Phase Transition to Nonbulk Morphology in Frustrated Films of Cylinder-Forming Polystyrene‑<i>b</i>‑polybutadiene Diblock Copolymers

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    Dimensions of cylindrical domains and microphase separation behavior in thin films of polystyrene-<i>b</i>-polybutadiene diblock copolymer (SB) are analyzed under fine variation of the surface fields, polymer–polymer interactions, film thickness, and the symmetry of the wetting conditions. In thermally and in solvent annealed films the dimensions of the closest to the substrate cylinders are smaller than both in thicker films and in bulk due to the confinement effect. The related excess of the stretching energy favors a transition to nonbulk perforated lamella morphology in a narrow window of the film thickness, solvent concentration, and annealing temperature. The discussion of the apparent stability/instability of thin film morphologies includes the analysis of molecular architecture, interfacial tensions, and possible influence of dynamic effects

    Enhancing Ordering Dynamics in Solvent-Annealed Block Copolymer Films by Lithographic Hard Mask Supports

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    We studied solvent-driven ordering dynamics of block copolymer films supported by a densely cross-linked polymer network designed as organic hard mask (HM) for lithographic fabrications. The ordering of microphase-separated domains at low degrees of swelling corresponding to intermediate/strong segregation regimes was found to proceed significantly faster in films on a HM layer as compared to similar block copolymer films on silicon wafers. The 10-fold enhancement of the chain mobility was evident in the dynamics of morphological phase transitions and of related process of terrace formation on a macroscale as well as in the degree of long-range lateral order of nanostructures. The effect is independent of the chemical structure and on the volume composition (cylinder/lamella forming) of the block copolymers. In-situ ellipsometric measurements of the swelling behavior revealed a cumulative increase in 1–3 vol % in solvent uptake by HM-block copolymer bilayer films, so that we suggest other than dilution effect reasons for the observed significant enhancement of the chain mobility in concentrated block copolymer solutions. Another beneficial effect of the HM-support is the suppression of the film dewetting which holds true even for low molecular weight homopolymer polystyrene films at high degrees of swelling. Apart from immediate technological impact in block copolymer-assisted nanolithography, our findings convey novel insight into effects of molecular architecture on polymer–solvent interactions

    Guiding Block Copolymers into Sequenced Patterns via Inverted Terrace Formation

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    Corrugated SiCN ceramic substrates fabricated by a facile replication process using nonlithographic PDMS masters were employed for the directed assembly of block copolymer microdomains. During thermal annealing of polystyrene-<i>b</i>-polybutadiene diblock copolymer, the material transport was guided by a wrinkled substrate to form regular modulations in the film thickness. As a consequence of the thickness-dependent morphological behavior of cylinder forming block copolymer, the film surface appears as sequenced patterns of alternative microphase-separated structures. The ordering process is attributed to the formation of inverted terraces which match the substrate topography, so that the resulting surface patterns are free from the surface relief structures within macroscopically large areas. The issues of the film thickness, the substrate surface energy, and the pattern geometry are addressed. Our approach demonstrates an effective synergism of external confinement and internal polymorphism of block copolymers toward complex hierarchically structured patterned surfaces

    Combined UV-Vis-absorbance and Reflectance Spectroscopy Study of Dye Transfer Kinetics in Aqueous Mixtures of Surfactants

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    <div> <div> <div> <p>We report an analytical approach to study the kinetics of desorption and exhaustion of a hydrophobic dye in a multicomponent washing model environment. The process of <b>dye transfer </b>between an acceptor textile (white polyamide), detergent micelles and a donor textile (red polyester) was quantified by a combination of colorimetric analyses.<b> UV-Vis absorbance and UV- reflectance </b>spectroscopy were used to follow the concentration of the solubilised dye in the micelles and the amount of dyer transferred to the acceptor textile, respectively, as a function of time. Up to ≃ 10 min of the washing process, the released dye is predominantly solubilised in surfactant micelles. At later times, the adsorption of the dye on the hydrophobic surface of the acceptor textile is energetically favoured. The shift of the desorption equilibrium in the presence of the acceptor textile results in ≃ 30% increase in the release of the dye. The reported methodology provides insight into the competition between solubilisation of hydrophobic molecules by amphiphiles and dye adsorption on solid substrates, important for designing novel concepts of dye transfer inhibition. </p> </div> </div> </div

    Combining Graphoepitaxy and Electric Fields toward Uniaxial Alignment of Solvent-Annealed Polystyrene–<i>b</i>–Poly(dimethylsiloxane) Block Copolymers

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    We report a combined directing effect of the simultaneously applied graphoepitaxy and electric field on the self-assembly of cylinder forming polystyrene-<i>b</i>-poly­(dimethylsiloxane) block copolymer in thin films. A correlation length of up to 20 μm of uniaxial ordered striped patterns is an order of magnitude greater than that produced by either graphoepitaxy or electric field alignment alone and is achieved at reduced annealing times. The angle between the electric field direction and the topographic guides as well as the dimensions of the trenches affected both the quality of the ordering and the direction of the orientation of cylindrical domains: parallel or perpendicular to the topographic features. We quantified the interplay between the electric field and the geometry of the topographic structures by constructing the phase diagram of microdomain orientation. This combined approach allows the fabrication of highly ordered block copolymer structures using macroscopically prepatterned photolithographic substrates