About the author

About the author

The author of this blog is a synthetic chemist working on silsesquioxanes and related organosilicon compounds, and on the functional hybrid materials that can be assembled from them.

Research interests

Daily work concerns the synthesis and selective functionalization of polyhedral oligomeric silsesquioxane cages of the T8 and T18 type, and the use of such platforms as rigid scaffolds for organic chromophores, catalytic sites, and polymer modifiers. Recurring questions include how the inorganic core governs the photophysical behavior of the attached organic units, how substitution patterns translate into thermal and mechanical performance, and how a synthetic route that works on a hundred milligram scale can be made reproducible on a much larger one.

Adjacent interests appear here from time to time. These include structural characterization by nuclear magnetic resonance spectroscopy of silicon and by single crystal diffraction, the practical limits of purification for compounds that resist crystallization, and the persistent gap between what a spectrum is claimed to show and what it actually supports.

Why this blog

Entries published here fall into three broad categories. The first consists of summaries of recently published studies, presented in language accessible to a reader from outside the field. The second comprises closer examinations of a single method, reagent, or instrumental technique, discussed in greater detail than the format of a research article would permit. The third is reserved for individual observations made in the course of laboratory work that appeared worth recording.

Everything published here is written by a working researcher.

Beyond the bench

Time outside synthesis goes to peer review, to the evaluation of research and innovation proposals, and to supervising early stage researchers as they learn to write. The habits acquired in those roles show up in the posts, mostly as an insistence that a claim should be stated precisely enough to be checked.

Contact

Questions about a specific preparation, requests for clarification of a published procedure, and corrections are all welcome. Comments left under the relevant post are the most useful channel, because the answer then remains available to the next reader with the same question.

Correspondence regarding published work is best directed to the address given in the corresponding paper. Everything else belongs in the comments.

Text and images published on this blog may be quoted only with attribution to the blog and a link to the original entry. Unauthorized use is not permitted, and any further reproduction, translation, or reuse requires prior written permission obtained by contacting the author.

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octa(3-aminopropyl)silsesquioxane

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Octa(3-aminopropyl)silsesquioxane hydrochloride (OAS) was first described in a patent filed by Wacker-Chemie GmbH. 1 That document, however, reports neither a method for its preparation nor the spectroscopic data required for its full identification. 2 Seven years later, Feher 3 investigated the hydrolytic condensation of (3-aminopropyl)triethoxysilane in methanolic solution, using hydrochloric acid as the catalyst, in order to obtain the octakis(3-aminopropyl)octasilsesquioxane chloride salt. Under these conditions the yield was 30% and the reaction required four weeks. Modifications of this procedure reported in the literature involve replacing the hydrolyzable group with a methoxy group or adding PtCl 4 as a cocatalyst, although such changes do not significantly increase the yield. 4–6 Kaneko and co-workers subsequently developed another valuable approach. 7 They examined the hydrolytic condensation of APTMS in the presence of a range of acid catalysts and found trifluoromethane...
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Structures of oligomeric silsesquioxanes (POSS)

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Polyhedral Silsesquioxanes Research on compounds containing the Si–O bond has long been dominated by silicon dioxide, by minerals built from repeating SiO₂ units, and by silicones composed of repeating R₂SiO units (R = alkyl or phenyl). Over the past 20 to 30 years, however, interest in silsesquioxanes based on the RSiO₁.₅ unit has increased markedly. Because these compounds contain both an inorganic fragment and an organic group, they display hybrid properties. The inorganic Si–O–Si framework imparts chemical and thermal resistance, whereas the organic R group enhances solubility and provides the required reactivity. A wide range of polymeric structures with the general formula (RSiO₁.₅)ₙ can be synthesized, although those adopting polyhedral architectures are of greatest interest. 4 Polyhedral oligomeric silsesquioxanes (POSS) are three-dimensional organosilicon compounds with the general empirical formula (RSiO₁.₅)ₙ , where R = H, alkyl, alkenyl, or aryl and n = 6, 8, 10, or 12. A w...
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T10-Type Decameric Silsesquioxanes: Synthesis, Cage Reorganization, and Properties of POSS

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Decameric silsesquioxanes of the T 10 cage type (general formula [RSiO 3/2 ] 10 ) represent a structurally distinct class of polyhedral oligomeric silsesquioxanes (POSS). Unlike the more common cubic T 8 cages possessing O h symmetry, T 10 silsesquioxanes adopt a prismatic cage geometry with idealized D 5h symmetry, in which ten silicon atoms are arranged in two parallel pentagonal rings connected by five bridging Si–O–Si linkages. Despite their interesting geometry and properties, T 10 silsesquioxanes are considerably less studied than their T 8 counterparts, primarily due to the challenges associated with their isolation in pure form. Topics covered in this post:  formation of T 10 POSS as a by-product of T 8 synthesis; cage reorganization pathways (nucleophilic substitution, fluoride-catalyzed, base-catalyzed, and superacid-mediated routes); separation and purification methods; crystal structure and D 5h symmetry; and spectroscopic and optical properties of T 10 de...
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