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Polyhedral Oligomeric Silsesquioxanes (POSS)—Synthesis, Functionalization, Applications

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

Deadline for manuscript submissions: closed (30 September 2021) | Viewed by 6532

Special Issue Editors


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Department of Chemistry and Technology of Polymers, Faculty of Chemical Engineering and Technology, Cracow University of Technology, ul. Warszawska 24, 31-155 Kraków, Poland
Interests: chemistry and technology of polymers; organic-inorganic hybrid materials; thermal degradation behavior; flame retardancy
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Guest Editor
Politechnika Krakowska, Krakow, Poland
Interests: polymer composites; biomaterials; nanocomposites; composites for medical applications; POSS; polyurethanes

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Guest Editor
Department of Chemistry and Technology of Polymers, Cracow University of Technology, ul. Warszawska 24, 31-155 Cracow, Poland
Interests: organic–inorganic hybrid materials and nanocomposites; stimuli-responsive polymers; glass transition; molecular dynamics; mechanical properties
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Polyhedral oligomeric silsesquioxanes (POSS) combine the best of the two worlds of inorganic and organic matter. As they consist of an inorganic core and an organic shell, one may refer to them as organic–inorganic hybrids. The core is a cage with silicon on its vertices and oxygen on its edges while the shell is composed of organic groups attached to the Si atoms. The vertex groups can be selected with remarkable versatility to accommodate different physical and chemical properties. With appropriate functionalization of the vertex groups, POSS can be applied as precursors in the synthesis of new nanomaterials or be incorporated in the organic polymer matrix as a reactive or inert filler. In that respect, functionalized POSS may serve as unique nanobuilding blocks in the synthesis of novel hybrid materials with improved characteristics over the traditional composites.

Functionalizations of POSS molecules have found their way into a diverse field of applications. They have been used as flame-retardant fillers or as reinforcing fillers in engineering polymers. Owing to their biocompatibility they have also been used in the biomedical field as components of dental fillings or tissue engineering scaffolds. They have also been proposed as drug delivery carriers, liquid crystals precursors, or catalysts.

This Special Issue will collect articles reporting on recent advances in the synthesis of various POSS molecules and their functionalization schemes. Furthermore, we would like to attract manuscripts on the applications of POSS, including but not limited to their role as reinforcing fillers for organic matrices, biomedical additives, and as catalysts. Interdisciplinary works that connect the chemistry of POSS molecules as nanobuilding blocks with materials science, physics, and biology-related approaches are particularly welcome.

Prof. Dr. Krzysztof Pielichowski
Dr. Edyta Hebda
Dr. Konstantinos N. Raftopoulos
Guest Editors

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Keywords

  • Polyhedral oligomeric silsesquioxane (POSS)
  • Organic–inorganic hybrid materials
  • Synthesis
  • Functionalization
  • Characterization
  • Applications

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Published Papers (2 papers)

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21 pages, 10878 KiB  
Article
PEG-POSS Star Molecules Blended in Polyurethane with Flexible Hard Segments: Morphology and Dynamics
by Konstantinos N. Raftopoulos, Edyta Hebda, Anna Grzybowska, Panagiotis A. Klonos, Apostolos Kyritsis and Krzysztof Pielichowski
Molecules 2021, 26(1), 99; https://doi.org/10.3390/molecules26010099 - 28 Dec 2020
Cited by 10 | Viewed by 2860
Abstract
A star polymer with a polyhedral oligomeric silsesquioxanne (POSS) core and poly(ethylene glycol) (PEG) vertex groups is incorporated in a polyurethane with flexible hard segments in-situ during the polymerization process. The blends are studied in terms of morphology, molecular dynamics, and charge mobility. [...] Read more.
A star polymer with a polyhedral oligomeric silsesquioxanne (POSS) core and poly(ethylene glycol) (PEG) vertex groups is incorporated in a polyurethane with flexible hard segments in-situ during the polymerization process. The blends are studied in terms of morphology, molecular dynamics, and charge mobility. The methods utilized for this purpose are scanning electron and atomic force microscopies (SEM, AFM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and to a larger extent dielectric relaxation spectroscopy (DRS). It is found that POSS reduces the degree of crystallinity of the hard segments. Contrary to what was observed in a similar system with POSS pendent along the main chain, soft phase calorimetric glass transition temperature drops as a result of plasticization, and homogenization of the soft phase by the star molecules. The dynamic glass transition though, remains practically unaffected, and a hypothesis is formed to resolve the discrepancy, based on the assumption of different thermal and dielectric responses of slow and fast modes of the system. A relaxation α′, slower than the bulky segmental α and common in polyurethanes, appears here too. A detailed analysis of dielectric spectra provides some evidence that this relaxation has cooperative character. An additional relaxation g, which is not commonly observed, accompanies the Maxwell Wagner Sillars interfacial polarization process, and has dynamics similar to it. POSS is found to introduce conductivity and possibly alter its mechanism. The study points out that different architectures of incorporation of POSS in polyurethane affect its physical properties by different mechanisms. Full article
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17 pages, 5587 KiB  
Article
Design, Preparation and Thermal Characterization of Polystyrene Composites Reinforced with Novel Three-Cages POSS Molecules
by Ignazio Blanco, Francesco Agatino Bottino, Gianluca Cicala, Giulia Ognibene and Claudio Tosto
Molecules 2020, 25(13), 2967; https://doi.org/10.3390/molecules25132967 - 28 Jun 2020
Cited by 3 | Viewed by 2497
Abstract
Novel polystyrene (PS)/polyhedral oligomeric silsequioxanes (POSSs) nanocomposites were designed and prepared by in situ polymerization, using, for the first time, three-cage POSS molecules. The synthesized compounds were first characterized by Fourier transform infrared spectroscopy (FTIR) and 1H NMR spectroscopy to verify the [...] Read more.
Novel polystyrene (PS)/polyhedral oligomeric silsequioxanes (POSSs) nanocomposites were designed and prepared by in situ polymerization, using, for the first time, three-cage POSS molecules. The synthesized compounds were first characterized by Fourier transform infrared spectroscopy (FTIR) and 1H NMR spectroscopy to verify the obtaining of the designed products before their thermal performance was evaluated and compared with those of pristine PS and the corresponding single-cage POSSs nanocomposites. The thermal behaviour was checked by the means of the differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) was also used to confirm the hypothesis about the dispersion/aggregation of the POSS molecules into the polymer matrix. The parameters chosen to evaluate the thermal stability of the investigated compounds, namely temperature at 5% of mass loss (T5%) and solid residue at 700 °C, showed a significant increase in the stability of the polymers reinforced with the three-cages POSS, in comparison to both PS and single-cage POSS reinforced PSs, which therefore turn out to be promising molecular fillers for nanocomposite production. Full article
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