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Special Issue "Mechanically Responsive Materials and Their Applications"

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Materials Chemistry".

Deadline for manuscript submissions: closed (31 July 2020).

Special Issue Editors

Prof. Dr. Elisabete C.B.A. Alegria
E-Mail Website
Guest Editor
1. Chemical Engineering Departament, Instituto Superior de Engenharia de Lisboa, Instituto Politécnico de Lisboa, Lisboa, Portugal
2. Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal
Interests: Sustainable homogeneous and supported catalysis; Green synthesis of metallic nanoparticles; mechanochemistry (synthesis and catalysis); molecular electrochemistry
Special Issues and Collections in MDPI journals
Dr. Maximilian N. Kopylovich
E-Mail Website
Guest Editor
Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal
Interests: coordination chemistry; metal-mediated (template) synthesis; catalysis; alcohol oxidation; nitrile transformation; mechanochemistry; noncovalent interactions

Special Issue Information

Dear Colleagues,

To adapt to the changing environment, biological systems employ specific stimuli-responsive molecules and supramolecular assemblies. Accordingly, the complex adaptation is possible due to the dynamic molecular tuning by regulating signals, e.g., specific compounds, temperature change, redox event or electromagnetic irradiation. Inspired by nature, chemists also implement controlling elements into the material design; for this purpose, adjustable structural units with properties controlled by a suitable stimulus are introduced to a responsive molecule. The respective molecular architectures that respond to external stimuli and alter their function are often referred to as smart materials, and mechanical action can be an attractive possibility to regulate properties of various materials.

In contrast to photochemical activation, the mechanical one can be achieved at dark and in nontransparent reaction mixtures. Moreover, its application does not require ferromagnetic components, as in the case of magnetically responsive materials. As opposed to the chemical triggers, the mechanical activation is noninvasive, noncumulative, and can be orthogonal to the reaction of interest. Furthermore, the mechanochemical transformation can be achieved in solid, is directional and regulated by the local molecular structure. This can lead to unusual molecular configurations and excitation states not accessible in solutions under convectional heating, irradiation, or electrical current. Last but not least, the mechanical activation is easy to achieve with relatively simple instrumentation and operational procedures.

For these reasons, elaboration and application of new mechanically responsive molecules, their aggregates, and related smart materials have become the focus of much attention, and this Special Issue is an attempt to provide a common ground for researches involved in the development of new materials receptive to mechanical stimuli. The application of such materials is limited only by our imagination, and it already involves enzyme mimics and modulation of reaction outcome, mechanoresponsive polymers and mechanosensitive channels, smart drug delivery and release, self-healing coatings, piezo- and triboelectric nanogenerators, to name but a few developments.

Prof. Dr. Elisabete C.B.A. Alegria
Dr. Maximilian N. Kopylovich
Guest Editors

Manuscript Submission Information

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. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short 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 thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly 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 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Mechanically responsive molecules
  • Stimuli-responsive materials
  • Dynamic molecular tuning
  • Smart materials
  • Dynamic catalysis
  • Smart drug delivery and release
  • Self-healing coatings
  • Mechanoresponsive polymers
  • Mechanosensitive channels
  • Piezoelectric materials
  • Triboelectric materials

Published Papers (3 papers)

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Research

Open AccessArticle
Ultrasound and Radiation-Induced Catalytic Oxidation of 1-Phenylethanol to Acetophenone with Iron-Containing Particulate Catalysts
Molecules 2020, 25(3), 740; https://doi.org/10.3390/molecules25030740 - 08 Feb 2020
Cited by 2 | Viewed by 857
Abstract
Iron-containing particulate catalysts of 0.1–1 µm size were prepared by wet and ball-milling procedures from common salts and characterized by FTIR, TGA, UV-Vis, PXRD, FEG-SEM, and XPS analyses. It was found that when the wet method was used, semi-spherical magnetic nanoparticles were formed, [...] Read more.
Iron-containing particulate catalysts of 0.1–1 µm size were prepared by wet and ball-milling procedures from common salts and characterized by FTIR, TGA, UV-Vis, PXRD, FEG-SEM, and XPS analyses. It was found that when the wet method was used, semi-spherical magnetic nanoparticles were formed, whereas the mechanochemical method resulted in the formation of nonmagnetic microscale needles and rectangles. Catalytic activity of the prepared materials in the oxidation of 1-phenylethanol to acetophenone was assessed under conventional heating, microwave (MW) irradiation, ultrasound (US), and oscillating magnetic field of high frequency (induction heating). In general, the catalysts obtained by wet methods exhibit lower activities, whereas the materials prepared by ball milling afford better acetophenone yields (up to 83%). A significant increase in yield (up to 4 times) was observed under the induction heating if compared to conventional heating. The study demonstrated that MW, US irradiations, and induction heating may have great potential as alternative ways to activate the catalytic system for alcohol oxidation. The possibility of the synthesized material to be magnetically recoverable has been also verified. Full article
(This article belongs to the Special Issue Mechanically Responsive Materials and Their Applications)
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Open AccessArticle
Introduction of Reversible Urethane Bonds Based on Vanillyl Alcohol for Efficient Self-Healing of Polyurethane Elastomers
Molecules 2019, 24(12), 2201; https://doi.org/10.3390/molecules24122201 - 12 Jun 2019
Cited by 5 | Viewed by 1326
Abstract
Urethane groups formed by reacting phenolic hydroxyl groups with isocyanates are known to be reversible at high temperatures. To investigate the intrinsic self-healing of polyurethane via a reversible urethane group, we synthesized vanillyl alcohol (VA)-based polyurethanes. The phenolic hydroxyl group of vanillyl alcohol [...] Read more.
Urethane groups formed by reacting phenolic hydroxyl groups with isocyanates are known to be reversible at high temperatures. To investigate the intrinsic self-healing of polyurethane via a reversible urethane group, we synthesized vanillyl alcohol (VA)-based polyurethanes. The phenolic hydroxyl group of vanillyl alcohol allows the introduction of a reversible urethane group into the polyurethane backbone. Particularly, we investigated the effects of varying the concentration of reversible urethane groups on the self-healing of the polyurethane, and we proposed a method that improved the mobility of the molecules contributing to the self-healing process. The concentration of reversible urethane groups in the polyurethanes was controlled by varying the vanillyl alcohol content. Increasing the concentration of the reversible urethane group worsened the self-healing property by increasing hydrogen bonding and microphase separation, which consequently decreased the molecular mobility. On the other hand, after formulating a modified chain extender (m-CE), hydrogen bonding and microphase separation decreased, and the mobility (and hence the self-healing efficiency) of the molecules improved. In VA40-10 (40% VA; 10% m-CE) heated to 140 °C, the self-healing efficiency reached 96.5% after 30 min, a 139% improvement over the control polyurethane elastomer (PU). We conclude that the self-healing and mechanical properties of polyurethanes might be tailored for applications by adjusting the vanillyl alcohol content and modifying the chain extender. Full article
(This article belongs to the Special Issue Mechanically Responsive Materials and Their Applications)
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Open AccessArticle
‘Seeing’ Strain in Soft Materials
Molecules 2019, 24(3), 542; https://doi.org/10.3390/molecules24030542 - 01 Feb 2019
Cited by 15 | Viewed by 1607
Abstract
Several technologies can be used for measuring strains of soft materials under high rate impact conditions. These technologies include high speed tensile test, split Hopkinson pressure bar test, digital image correlation and high speed X-ray imaging. However, none of these existing technologies can [...] Read more.
Several technologies can be used for measuring strains of soft materials under high rate impact conditions. These technologies include high speed tensile test, split Hopkinson pressure bar test, digital image correlation and high speed X-ray imaging. However, none of these existing technologies can produce a continuous 3D spatial strain distribution in the test specimen. Here we report a novel passive strain sensor based on poly(dimethyl siloxane) (PDMS) elastomer with covalently incorporated spiropyran (SP) mechanophore to measure impact induced strains. We have shown that the incorporation of SP into PDMS at 0.25 wt% level can adequately measure impact strains via color change under a high strain rate of 1500 s−1 within a fraction of a millisecond. Further, the color change is fully reversible and thus can be used repeatedly. This technology has a high potential to be used for quantifying brain strain for traumatic brain injury applications. Full article
(This article belongs to the Special Issue Mechanically Responsive Materials and Their Applications)
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