Tetraethyl orthosilicate c8h20o4si

All solvents and reagents were purchased from commercial sources and used as received for preparing the cyclic carbonates, the SiO₂ nanoparticles, and the polymers. 1,2-Epoxybutane (C₄H₈O), aniline (C₆H₇N) and dimethylformamide were supplied by Sigma Aldrich (Toluca, México), with a purity of 99%, ≥99.5 and 99.8%, respectively. Poly(vinyl alcohol) ((CH₂CHOH)_n < 99%) and 1,6-hexamethylenediamine (C₆H₁₆N₂, 98%) were purchased from Aldrich and lithium chloride (LiCl, <99.69%) from CTR Scientific (Monterrey, México). For silica nanoparticles, tetraethyl orthosilicate (C₈H₂₀O₄Si) with a purity of 98% was provided by Sigma Aldrich, ammonium hydroxide (NH₄OH, 28.7%) by Fermont (Monterrey, México) and ethyl alcohol (CH₃CH₂OH, 96%) supplied by Golden Bell (Jalisco, México). All reactants were used without further purification. The experiments were carried out in a 100 mL beaker as a closed system, according to the times and set temperatures. Nuclear magnetic resonance spectroscopy (¹H-NMR), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible absorption spectroscopy (UV-Vis) and scanning electron microscopy (SEM), besides thermogravimetric analysis (TGA), derivative thermogravimetric analysis (DTG) and a transient line heat source method, were the characterization techniques applied in this research.

For powder synthesis, analytical grade chemicals were used, as SiO₂, P₂O₅, CaO, ZnO and MgO sources, these being purchased from Sigma Aldrich, Steinheim, Germany: tetraethyl orthosilicate (C₈H₂₀O₄Si, TEOS; 99%), triethyl phosphate (C₂H₅O)₃PO, TEP; >98%), calcium nitrate tetrahydrate (Ca(NO₃)₂·4H₂O; ≥99), zinc acetate dihydrate (Zn(CH₃COO)₂·2H₂O; >98%), and magnesium nitrate hexahydrate (Mg(NO₃)₂·6H₂O; >99), hydrochloric acid (HCl; 1N), isopropyl alcohol (C₃H₇-OH; >99%). Additionally, the following chemicals were used: Pluronic^® F127 (HO(CH₂-CH₂-O)₁₀₀(CH(CH₃)CH₂-O)₆₅(CH₂CH₂O)₁₀₀H; 99%, Sigma-Aldrich, Darmstadt, Germany) and distilled water.