Polyhedral Oligomeric Silsesquioxane (POSS) Chemistry

Amide-POSS acyl chloride synthesis, developed by Mateusz Janeta and Sławomir Szafert at the University of Wrocław and reported in Chemistry – A European Journal in 2014, achieves homoocta-substituted amido-functionalized polyhedral oligomeric silsesquioxane (POSS) in isolated yields of approximately 95%, substantially exceeding the ca. 60% ceiling typically attainable by conventional carboxylic acid or anhydride routes. The strategy relies on crystalline ionic octa(3-aminopropyl)silsesquioxane (OAS-POSS) salts as scaffold precursors, reacted with aryl and alkyl acyl chlorides under mild conditions in the presence of triethylamine. The resulting amide-POSS compounds spontaneously self-organize into discrete spherical nanoparticles approximately 5 nm in diameter, as confirmed by transmission electron microscopy. Polyhedral oligomeric silsesquioxanes (POSS) constitute a class of organosilicon cage compounds with the general formula (RSiO 3/2 ) 8 , wherein eight silicon atoms are brid...

Polyhedral oligomeric silsesquioxanes (POSS) possess a unique inorganic–organic hybrid architecture in which a rigid Si–O–Si cage is covalently bonded to peripheral organic substituents. The presence of Si–O bonds in the central core imparts exceptional thermal, mechanical, and chemical stability, making these compounds highly attractive from an industrial standpoint. Among the many technologically relevant properties of POSS, their ability to improve the oxidation resistance of POSS-doped polymer matrices has received particular attention. For this reason, a thorough understanding of the thermal behavior of POSS and its dependence on T8 and T10 silsesquioxane cage structure and organic functionalization has become an important research objective in the field of organosilicon chemistry. Topics covered in this post: thermal stability of POSS cage compounds and the influence of organic substituents on decomposition temperature; thermogravimetric analysis under inert and oxidativ...

Amide derivatives of octa(3-aminopropyl)silsesquioxane (OAS-POSS) rank among the most useful organic–inorganic hybrids that can be assembled on a cubic siloxane core. Conventional routes to these compounds rely on carboxylic acids activated by coupling agents such as DCC, or on acid anhydrides, and rarely exceed roughly 60 % yield. Janeta and co-workers ( Chem. – Eur. J. 2014 , 20 , 15966–15974 ) demonstrated that acyl chlorides offer a decisively better alternative, furnishing homosubstituted amide-POSS in yields approaching 95 % while leaving the (RSiO 3/2 ) 8 framework intact. Ionic precursors as stable scaffolds Neutral octa(3-aminopropyl)silsesquioxane is inconvenient to store, because it evolves continuously in solution and is prone to opening of the cage. Three crystalline ammonium salts were therefore prepared in a one-step hydrolytic condensation of (3-aminopropyl)triethoxysilane (APTES) with hydrochloric acid (3.6 equiv), trifluoromethanesulf...