Synthesis and Characterization of Polyhedral Silsesquioxanes Bearing Bulky Functionalized Substituents

Abstract

A simple route to synthesize polyhedral silsesquioxanes, (RSiO1.5) n , by the hydrolytic condensation of modified aminosilanes, is reported. The starting material was N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, a trifunctional aminosilane. It was reacted with a stoichiometric amount of phenylglycidyl ether in sealed ampules at 50 °C for 24 h, leading to the trisubstituted product plus a series of oligomers arising from the intermolecular reaction between methoxysilane groups and the secondary hydroxyls generated by the epoxy−amine reaction. When this product was subjected to hydrolytic condensation using a variety of catalysts (HCl, NaOH, HCOOH) and a thermal cycle attaining 150 °C, polyhedral silsesquioxanes (SSQO) were obtained. Their molar mass was independent of reaction conditions as revealed by size exclusion chromatography. Characterization by 1H, 13C, and 29Si NMR suggested that the main product was a mixture of polyhedral SSQO with n = 8 and 10; i.e., T8 and T10. Due to the high OH functionality, i.e., 24 OH groups in T8 and 30 OH groups in T10 polyhedra, the synthesized product may be used as a cross-linking unit of very high functionality or as a modifier for several polymeric materials.

Architecture of Silsesquioxanes

“…3) and were obtained by a careful choice of the organic group promoting intramolecular cyclization and condensation conditions. Fasce et al reported similar considerations on cage-type silsesquioxanes with 8, 9, and 10 Si atoms, obtained by the hydrolytic condensation of triethoxysilanes with bulky organic substituents (Fasce et al 1999(Fasce et al , 2001. The presence of (β-hydroxyl) tertiary amine functions in the bulky organic group of the pristine organosilane favored the formation of closed structures (Dell'Erba et al 2003;Fasce et al 2005).…”

Preparation and thermal property of hybrid nanocomposites by free radical copolymerization of styrene with octavinyl polyhedral oligomeric silsesquioxane

“…The structures of the PS-POSS hybrid nanocomposites were well characterized by FTIR, 1 H NMR, and 29 Si NMR, which proved that the resultant nanocomposites were of star and low cross-linking structures. The thermal properties of the PS-POSS hybrid nanocomposites were studied by the DSC and TGA techniques.…”

“…The high-resolution 29 Si NMR spectroscopy provides further insight to the copolymerization of styrene with the POSS macromonomers. Figure 4 shows the 29 Si NMR spectra of both pure POSS macromonomer and PS-POSS nanocomposite (2.21 mol % POSS).…”

“…Figure 4 shows the 29 Si NMR spectra of both pure POSS macromonomer and PS-POSS nanocomposite (2.21 mol % POSS). For pure octavinyl-POSS, there is only one resonance peak at 279.5 ppm, because all silicon atoms have the same chemical environment in the POSS cages.…”

“…1 H NMR spectra were recorded on a Bruker AVANCE/DMX 300 spectrometer using chloroform-d solvent. High-resolution 29 Si NMR spectra were carried out at room temperature using a Bruker DSX-400 spectrometer operating at resonance frequency of 79.49 MHz. Weight-average (M w ) and number-average (M n ) molecular weights and polydispersity index (PDI, M w /M n ) were determined by a Waters 515 gel permeation chromatograph (GPC).…”