Thermal behavior and dehydration kinetic study of SiO₂/PEG hybrid gel glasses

Abstract

Six different silica‐polyethylene glycol (SiO2/PEG) organic‐inorganic hybrid nanocomposites with different amounts of PEG 400 (6, 12, 24, 50, 60 and 70 wt.%) were synthesized by the sol‐gel technique. Their thermal behavior was studied by thermogravimetry (TG) and differential thermal analysis (DTA) under a flowing argon atmosphere in a wide temperature range and their behavior was compared with those of the related materials with 60 and 70 wt.% of PEG, whose results were reported in a previously study. To identify all physical and chemical processes occurring in these promising materials, the gases evolved during TG experiments were analyzed at characteristic constant temperatures by FTIR. These measurements revealed that all the materials undergo a two‐step dehydration (loosing water physically bound at temperature lower than 100°C) with overlapping of both TG and DTA curves, thus suggesting an identical behavior up to 200°C regardless the different content of PEG. A different behavior is observed at higher temperature, where three different exothermic effects were observed in the range 200–450°C accompanied by mass losses ranging from 6 to 37% for the SiO2/PEG hybrid materials. POLYM. ENG. SCI., 57:606–612, 2017. © 2017 Society of Plastics Engineers

Thermal Behavior and Structural Study of SiO2/Poly(ε-caprolactone) Hybrids Synthesized via Sol-Gel Method

“…The TG/DSC curves of all the materials in Figure 1 showed an initial mass loss (corresponding to the first DTG peak) accompanied by an endothermic DSC peak, ascribed to the simultaneous loss of water and alcohol up to 140 °C, except for SP50 (short dotted lines) for which the process ends at around 85 °C. It is clearly evident from Figure 2 (low-temperature region) that the SP hybrid materials, except for SP24 and SP50, show the same thermal behavior as pure S. At temperature higher than 180 °C, dehydration is completed and S undergoes dehydroxylation, elimination of water due to condensation of the hydroxyl surface groups, with a slow and quite constant mass loss rate (linear portion of the TG curve up to 600 °C not detectable by the DTG curve), as found in previous studies [ 19 , 20 , 21 , 22 , 24 , 25 ]. SP materials (except for SP24 and SP50) show the same thermal behavior up to 300–400 °C, while at higher temperatures, a one- or two-step process took place up to 580–600 °C.…”

“…Recently, silica-based organic-inorganic hybrids have been attracting the growing interest of several research groups, leading to the development of functional materials for many application areas [ 14 , 15 , 16 , 17 , 18 ]. In the last two–three years, our group has also been involved in preparing (via the sol-gel method) and characterizing SiO 2 -based glasses, ceramics [ 19 , 20 , 21 , 22 , 23 ], as well as SiO 2 -based OIHs, with particular reference to SiO 2 /polyethylene glycol (SiO 2 /PEG) hybrids containing increasing percentages of PEG (from 6 to 70 wt %) [ 24 , 25 ]. More recently, SiO 2 /PCL hybrids containing variable percentages of PCL (6, 12, 24 and 50 wt %) were synthesized via sol-gel and characterized by means of several instrumental techniques [ 26 ].…”

Sol–gel synthesis and thermal behavior of bioactive ferrous citrate–silica hybrid materials

“…5. As already shown in our recent studies [40,41], pure SiO 2 undergoes dehydration up to 100°C, followed by dehydroxylation, a slow release of water due to condensation of surface hydroxyl groups of the inorganic matrix up to 500°C. Pure Fe(II)C losses only 1.1% of dehydration water up to 140°C, and a remarkable three-step degradation takes place between 150 and 500°C, being the first one associated to 50.5% of mass loss.…”

Sol–Gel Synthesis of Silica-Based Materials with Different Percentages of PEG or PCL and High Chlorogenic Acid Content

“…When different amounts of PEG were added in the materials (Figure 3), the bands of methylene C–H stretching and bending at 2930–2870 cm −1 and 1454 cm −1 are clearly detectible in all spectra, furthermore, its intensity increased with increasing polymer amount [37]. The characteristic C–O stretching band at 1250 cm −1 is evident only when a high amount of PEG was added in the hybrid [38]. Indeed, the presence of PCL in the materials (Figure 4) determines the appearance of typical peaks not visible in Figure 3.…”