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Preparation and Characterization of Highly Cross-Linked Polyimide Aerogels Based on Polyimide Containing Trimethoxysilane Side Groups
journal contribution
posted on 2014-11-11, 00:00 authored by Xueliang Pei, Wentao Zhai, Wenge ZhengIn
this study, highly cross-linked and completely imidized polyimide
aerogels were prepared from polyimide containing trimethoxysilane
side groups, which was obtained as the condensation product of polyimide
containing acid chloride side groups and 3-aminopropyltrimethoxysilane.
After adding water and acid catalyst, the trimethoxysilane side groups
hydrolyzed and condensed one another, and a continuous increase in
the complex viscosities of the polyimide solutions with time was observed.
The formed polyimide gels were dried by freeze-drying from tert-butyl alcohol to obtain polyimide aerogels, which consisted
of a three-dimensional network of polyimide fibers tangled together.
By varying the solution concentration of the polyimide containing
trimethoxysilane side groups, polyimide aerogels with different densities
(ranging from 0.19 to 0.42 g/cm3) were obtained. The resulting
polyimide aerogels had small pore diameter (ranging from 20.7 to 58.3
nm), high surface area (ranging from 310 to 344 m2/g),
high 5% weight loss temperature in air (at about 440 °C), and
an excellent mechanical property. In addition, the glass transition
temperature (349 °C) of the polyimide aerogels was much higher
than that (210 °C) of the corresponding linear polyimide. So,
even after being heated at 300 °C for 30 min, the porous structure
of the polyimide aerogels was not completely destroyed.