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X-ray crystal structures, packing behavior and thermal stability studies of a homologous series of n-alkyl-substituted polyhedral oligomeric silsesquioxanes

El Aziz, Youssef; Bassindale, Alan R.; Taylor, Peter G.; Stephenson, Richard A.; Hursthouse, Michael B.; Harrington, Ross W. and Clegg, William (2013). X-ray crystal structures, packing behavior and thermal stability studies of a homologous series of n-alkyl-substituted polyhedral oligomeric silsesquioxanes. Macromolecules, 46(3) pp. 988–1001.

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DOI (Digital Object Identifier) Link: https://doi.org/10.1021/ma302229v
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Abstract

The homologous series of octa-n-alkylsilsesquioxanes (n-alkylPOSS) was prepared by hydrosilylation of octahydrido-octasilsesquioxane H8T8 with terminal n-alkenes in good yields (n = 2–18). The compounds were characterized by NMR spectroscopy (1H, 13C, 29Si), MALDI-TOF and ESI MS. Most of them have also been characterized using X-ray crystallography, including some polymorphs. The packing systems of the octa-n-alkylsilsesquioxanes are reported. Two types of packing have been observed, rod-like and disk-like (interdigitated). Some n-alkylPOSS crystals were formed in which the chains are tilted away from the axes of the cubic core. It was also observed that as alkyl-chains are flexible they can take up a variety of conformations. Melting points of the homologous series showed an odd-even alternating effect for alkyl chains longer than four CH2 units. The TGA of n-alkylPOSS under nitrogen showed that the thermal stability temperatures are between 200 and 400 °C. Pyrolysis-gas chromatography/mass spectrometry has been used to elucidate the thermal degradation process of T8(n-CnH2n+1)8 (n = 11 and 18). Thermal cracking along the whole alkyl chain was observed rather than simple loss of the complete arm.

Item Type: Journal Item
Copyright Holders: 2013 American Chemical Society
ISSN: 1520-5835
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Life, Health and Chemical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Other Departments > Vice-Chancellor's Office
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Item ID: 35986
Depositing User: Peter Taylor
Date Deposited: 11 Jan 2013 10:39
Last Modified: 07 Dec 2018 10:39
URI: http://oro.open.ac.uk/id/eprint/35986
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