New Aminophenylsilsesquioxanes—Synthesis, Properties, and Epoxy Nanocomposites

Abstract

New aminophenylsilsesquioxanes, dodecaaminophenylsilsesquioxane (NH2PhSiO1.5)12 (DAPS), and hexadecaaminooctaphenylsilsesquioxane ((NH2)2PhSiO1.5)8 (HDAPS), were prepared from dodecaphenylsilsesquioxane (PhSiO1.5)12 (DPS), and octaphenylsilsesquioxane (PhSiO1.5)8 (OPS), by nitration in fuming HNO3, followed by reduction with HCO2H/Et3N/Pd/C. The effects of the cage structure and numbers of NH2 groups on the chemical and physical properties of these compounds were compared with octaaminophenylsilsesquioxane (NH2PhSiO1.5)8 (OAPS), and analogous epoxy resin nanocomposites. The cage structure does not affect nitration patterns (primarily meta and para), but affects coefficients of thermal expansion (CTEs), likely because of overall crosslink densities and because of the epoxy tether structures joining cube vertices. CTEs as low as 25 ± 2 ppm°C–1 were found, perhaps the lowest reported for an unfilled epoxy resin. The thermal stabilities of synthesized HDAPS epoxy nanocomposites were 20–30°C lower than those made with OAPS. This result may be a consequence of less-complete curing due to gelation before stoichiometric curing, caused by the much higher crosslink densities in OAPS.

Synthesis and characterization of organic/inorganic epoxy nanocomposites from poly(aminopropyl/phenyl)silsesquioxanes

“…The incorporation of organic/inorganic silsesquioxanes (SQs) into polymer matrices has been extensively investigated to improve nanocomposites properties due to the intrinsic properties of SQs including nanometer dimensions, low densities, excellent heat, and fire‐resistant properties as well as the ability to tailor the types and amounts of functional groups. SQs generally consist of silicon‐oxygen cores with (SiO 1.5 ) n abbreviated T n, where n = 6, 8, 10, 12 along with pendant organic substituents (R) such as phenyl,19 vinyl,20 amine,21–25 epoxy,26–29 and arylhalide30,31 depending on the final required chemical structure and target properties required of the specific application.…”

Octakis(3‐azidopropyl)octasilsesquioxane: A Versatile Nanobuilding Block for the Efficient Preparation of Highly Functionalized Cube‐Octameric Polyhedral Oligosilsesquioxane Frameworks Through Click Assembly

“…Keywords: azides · carbohydrates · click chemistry · dyes/pigments · silsesquioxanes reactions are suited for this purpose, although care must be taken to avoid strongly acidic, basic, or oxidizing environments that can compromise the stability of the POSS cage. Transition metal-catalyzed reactions such as hydrosilylation, [14,-19-29] olefin cross-metathesis, [28,[30][31][32] and Heck, [28,[33][34][35][36][37] Suzuki, [28,36] or Sonogashira [28,36] couplings; acylation [21,[38][39][40][41] and Michael addition [21,42] reactions of amines; electrophilic aromatic substitution reactions; [36,[43][44][45][46][47] nucleophilic substitution of halogen; [14,17,[48][49][50] and radical addition of thiols [51,52] or R 2 PH [53][54][55] to olefins, have been used for this purpose with great success. Surprisingly, the copper(I)-catalyzed 1,3dipolar Huisgen cycloaddition of azides to alkynes (CuAAC), [56][57][58] a paradigmatic example of a "click reaction", [59] which is a robust and reliable method for the efficient functionalization of a wide variety of molecules under mild condition...…”

Polyphenylsilsesquioxanes. New structures–new properties

“…Incorporation of functional groups into the organic component by electrophilic substitution reactions allows p-PPSQ to be subsequently used for synthesizing a variety of compounds. The most common of these reactions are nitration 76,77 followed by reduction to an amino group, as well as halogenation. [78][79][80][81] The feasibility of performing this reaction is rather unusual.…”