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Hybrid Sol–Gel Glasses with Glass‐Transition Temperatures Below Room Temperature
Author(s) -
Jitianu Andrei,
Gonzalez Guadalupe,
Klein Lisa C.
Publication year - 2015
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.13798
Subject(s) - glass transition , differential scanning calorimetry , gravimetric analysis , chemistry , thermogravimetric analysis , melting temperature , thermal analysis , analytical chemistry (journal) , differential thermal analysis , melting point , polymer chemistry , materials science , thermal , chromatography , thermodynamics , polymer , organic chemistry , composite material , physics , diffraction , optics
Melting gels are hybrid gels that have the ability to soften and flow at around 100°C for some combinations of mono‐ and di‐substituted alkoxysiloxanes, where substitutions are either all aromatic or all aliphatic. In this study, melting gels were prepared using phenyltriethoxysilane (PhTES) and dimethyldiethoxysilane (DMDES), meaning both an aromatic and aliphatic substitution. Differential scanning calorimetry was performed to identify glass‐transition temperatures, and thermal gravimetric analysis coupled with differential thermal analysis ( TGA ‐ DTA ) was performed to measure weight loss. The glass‐transition temperatures ( T g ) ranged from −61°C to +5.6°C, which are between the values in the methyl only system, where all T g values are less than 0°C, and those values in the phenyl only system, where T g values are greater than 0°C. The T g decreased with an increase in the DMDES fraction. Below 450°C, the gels lost little weight, but around 600°C there was a drop in weight. This temperature is lower than the temperature for gels prepared with only aromatic substitutions, but higher than that for gels prepared with only aliphatic substitutions. Final heat treatment was carried out at 150°C for the gel with 80%Ph TES ‐20% DMDES (in mol%), and the consolidation temperature increased with increasing DMDES content to 205°C for the gel with 50%Ph TES ‐50% DMDES . After this heat treatment, the melting gels no longer soften.