Special Issue "Nano-Structures of Block Copolymers"
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A special issue of Polymers (ISSN 2073-4360).
Deadline for manuscript submissions: closed (31 August 2010)
Special Issue Editor
Guest Editor
Prof. Dr. Alexander Böker
DWI an der RWTH Aachen e.V., Lehrstuhl für Makromolekulare Materialien und Oberflächen, Forckenbeckstrasse 50, D-52056 Aachen, Germany
Website: http://www.ipc.rwth-aachen.de/boeker
E-Mail: boeker@dwi.rwth-aachen.de
Phone: +49 241 80 23304
Fax: +49 241 80 23317
Interests: guided block copolymer assembly; orientation and phase behavior of block copolymers in electric fields; block copolymer/nanoparticle composites; self-assembly of nanoparticles at interfaces; Pickering-Emulsions; template directed nanoparticle assembly; pattern transfer
Special Issue Information
Dear Colleagues,
Block copolymers, their microphase separation as well as their resulting nanoscopic structures have been studied extensively over the past three decades both experimentally and theoretically. Despite considerable efforts and promising results, so far industrially relevant technologies based on block copolymer nanostructures have not yet been developed or at least did not make it to the final product.
This special issue is intended to give the reader an overview over recent cutting edge research and new developments in the field of block copolymer nanotechnology. Here, we would like to place emphasis on work dealing with ways to control and guide the self-assembly of block copolymer systems, the introduction of functionality, block copolymer-based templates, block copolymer hybrid systems, and novel morphologies arising from these hybrid materials. Finally, this issue should also give examples how block copolymer nanostructures can help to meet future requirements in fields like e.g. electronics, data storage as well as energy storage and conversion.
Prof. Dr. Alexander Böker
Guest Editor
Submission
Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.
Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed Open Access quarterly journal published by MDPI.
Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 500 CHF (Swiss Francs).
English correction and/or formatting fees of 250 CHF (Swiss Francs) will be charged in certain cases for those articles accepted for publication that require extensive additional formatting and/or English corrections.
Keywords
- functional block copolymers
- controlled self-assembly
- external/internal fields
- control of order
- hybrid materials
- block copolymer-based applications
Published Papers (9 papers)
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Received: 31 August 2010; in revised form: 8 October 2010 / Accepted: 14 October 2010 / Published: 15 October 2010
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Abstract: Block copolymers are versatile designer macromolecules where a “bottom-up” approach can be used to create tailored materials with unique properties. These simple building blocks allow us to create actuators that convert energy from a variety of sources (such as chemical, electrical and heat) into mechanical energy. In this review we will discuss the advantages and potential pitfalls of using block copolymers to create actuators, putting emphasis on the ways in which these materials can be synthesised and processed. Particular attention will be given to the theoretical background of microphase separation and how the phase diagram can be used during the design process of actuators. Different types of actuation will be discussed throughout.
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Received: 24 August 2010; in revised form: 25 September 2010 / Accepted: 15 October 2010 / Published: 20 October 2010
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Abstract: Nanostructures generated from block copolymer self-assembly enable a variety of potential technological applications. In this article we review recent work and the current status of two major emerging applications of block copolymer (BCP) nanostructures: lithography for microelectronics and photovoltaics. We review the progress in BCP lithography in relation to the requirements of the semiconductor technology roadmap. For photovoltaic applications, we review the current status of the quest to generate ideal nanostructures using BCPs and directions for future research.
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Received: 28 September 2010; in revised form: 18 October 2010 / Accepted: 21 October 2010 / Published: 25 October 2010
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Abstract: We fabricated titanium dioxide (TiO2)-silica (SiO2) nanocomposite structures with controlled morphology by a simple synthetic approach using cooperative sol-gel chemistry and block copolymer (BCP) self-assembly. Mixed TiO2-SiO2 sol-gel precursors were blended with amphiphilic poly(styrene-block-ethylene oxide) (PS-b-PEO) BCPs where the precursors were selectively incorporated into the hydrophilic PEO domains. Changing the volumetric ratio of TiO2-SiO2 sol-gel precursor from 5% to 20%, a stepwise structural inversion occurred from nanodot arrays to discrete nanowires. Template free hybrid inorganic nanostructures were produced after the removal of PS-b-PEO by irradiation of UV light. The morphological evolution and photophysical properties were investigated by microscopic studies, UV-visible absorption and photocatalytic properties.
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Received: 9 November 2010; in revised form: 15 November 2010 / Accepted: 24 November 2010 / Published: 25 November 2010
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Abstract: Dendrigraft polymers have a multi-level branched architecture resulting from the covalent assembly of macromolecular building blocks. Most of these materials are obtained in divergent (core-first) synthetic procedures whereby the molecule grows outwards in successive grafting reactions or generations. Two main types of dendrigraft polymers can be identified depending on the distribution of reactive sites over the grafting substrate: Arborescent polymers have a large and variable number of more or less uniformly distributed sites, while dendrimer-like star polymers have a lower but well-defined number of grafting sites strictly located at the ends of the substrate chains. An overview of the synthesis and the characterization of dendrigraft copolymers with phase-segregated morphologies is provided in this review for both dendrigraft polymer families. The tethering of side-chains with a different composition onto branched substrates confers unusual physical properties to these copolymers, which are highlighted through selected examples.
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Received: 2 September 2010; in revised form: 31 October 2010 / Accepted: 26 November 2010 / Published: 2 December 2010
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Abstract: Selectively plasma-etched polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer masks present a promising alternative for subsequent nanoscale patterning of underlying films. Because mask roughness can be detrimental to pattern transfer, this study examines roughness formation, with a focus on the role of cross-linking, during plasma etching of PS and PMMA. Variables include ion bombardment energy, polymer molecular weight and etch gas mixture. Roughness data support a proposed model in which surface roughness is attributed to polymer aggregation associated with cross-linking induced by energetic ion bombardment. In this model, RMS roughness peaks when cross-linking rates are comparable to chain scissioning rates, and drop to negligible levels for either very low or very high rates of cross-linking. Aggregation is minimal for very low rates of cross-linking, while very high rates produce a continuous cross-linked surface layer with low roughness. Molecular weight shows a negligible effect on roughness, while the introduction of H and F atoms suppresses roughness, apparently by terminating dangling bonds. For PS etched in Ar/O2 plasmas, roughness decreases with increasing ion energy are tentatively attributed to the formation of a continuous cross-linked layer, while roughness increases with ion energy for PMMA are attributed to increases in cross-linking from negligible to moderate levels.
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Received: 26 October 2010; in revised form: 14 December 2010 / Accepted: 22 December 2010 / Published: 27 December 2010
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Abstract: Block copolymers forming glassy spheres in the matrix of rubbery chains can exhibit elastomeric properties. It is well known that the spherical microdomains are arranged in the body-center cubic (bcc) lattice. However, recently, we have found packing in the face-centered cubic (fcc) lattice, which is easily transformed into the bcc lattice upon uniaxial stretching. In the same time, the packing regularity of the spheres in the bcc lattice was found to be enhanced for samples completely recovered from the stretched state. This reminds us that a cycle of stretching-and-releasing plays an important role from analogy of densification of the packing in granules upon shaking. In the current paper, we quantify the enhancement of packing regularity of spherical microdomains in the bcc lattice upon uniaxial stretching of the same elastomeric triblock copolymer as used in our previous work by conducting small-angle X-ray scattering (SAXS) measurements using high brilliant synchrotron radiation. Isotropically circular rings of the lattice peaks observed for the unstretched sample turned into deformed ellipsoidal rings upon the uniaxial stretching, with sharpening of the peaks in the direction parallel to the stretching direction and almost disappearing of the peaks in the perpendicular direction. By quantitatively analyzing the SAXS results, it was found that the packing regularity of the spherical microdomains was enhanced in the parallel direction while it was spoiled in the perpendicular direction under the stretched state. The enhanced regularity of packing was unchanged even if the stretching load was completely removed.
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Received: 30 November 2010; in revised form: 20 December 2010 / Accepted: 29 December 2010 / Published: 11 January 2011
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Abstract: In dilute aqueous solutions certain amphiphilic block copolymers self-assemble into vesicles that enclose a small pool of water with a membrane. Such polymersomes have promising applications ranging from targeted drug-delivery devices, to biosensors, and nanoreactors. Interactions between block copolymer membranes and their surroundings are important factors that determine their potential biomedical applications. Such interactions are influenced predominantly by the membrane surface. We review methods to functionalize block copolymer vesicle surfaces by chemical means with ligands such as antibodies, adhesion moieties, enzymes, carbohydrates and fluorophores. Furthermore, surface-functionalization can be achieved by self-assembly of polymers that carry ligands at their chain ends or in their hydrophilic blocks. While this review focuses on the strategies to functionalize vesicle surfaces, the applications realized by, and envisioned for, such functional polymersomes are also highlighted.
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Received: 30 November 2010; in revised form: 22 December 2010 / Accepted: 5 January 2011 / Published: 11 January 2011
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Abstract: Concentrated solutions of a water-soluble block copolymer (PEO)20-(PPO)70-(PEO)20 show a thermoreversible transition from a liquid to a gel. Over a range of concentration there also exists an order-order transition (OOT) between cubically-packed spherical micelles and hexagonally-packed cylindrical micelles. This OOT displays a hysteresis between the heating and cooling transitions that is observed at both the macroscale through rheology and nanoscale through small angle neutron scattering (SANS). The hysteresis is caused by the persistence of the cubically-packed spherical micelle phase into the hexagonally-packed cylindrical micelle phase likely due to the hindered realignment of the spherical micelles into cylindrical micelles and then packing of the cylindrical micelles into a hexagonally-packed cylindrical micelle phase. This type of hysteresis must be fully characterized, and possibly avoided, for these block copolymer systems to be used as templates in nanocomposites.
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Received: 28 January 2011 / Accepted: 28 February 2011 / Published: 24 March 2011
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Abstract: Nanoparticles can self-assemble into highly ordered two- and three-dimensional superlattices. For many practical applications these assemblies need to be integrated into polymeric matrices to provide stability and function. By appropriate co-assembly of nanoparticles and polymers it has become possible to tailor the nanoparticle superlattice structure via the length and stiffness of the polymer chains. The present article outlines and discusses established routes to nanoparticle-polymer superlattices. Recent progress has been remarkable so that the integration into functional devices has become the next challenge.
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Last update: 13 January 2011
