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Polyimide–Silica Gel Hybrids Containing Metal Salts: Preparation via the Sol–Gel Reaction
Author(s) -
Avadhani C. V.,
Chujo Y.
Publication year - 1997
Publication title -
applied organometallic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 71
eISSN - 1099-0739
pISSN - 0268-2605
DOI - 10.1002/(sici)1099-0739(199702)11:2<153::aid-aoc563>3.0.co;2-w
Subject(s) - pyromellitic dianhydride , isocyanate , polyimide , chemistry , polymer chemistry , condensation polymer , silica gel , hybrid material , hydrolysis , organic chemistry , polyurethane , catalysis , layer (electronics)
A facile preparation of polyimide–silica gel hybrids by the simultaneous in‐situ formation of polyimides during the hydrolysis–condensation of tetramethoxysilane (TMOS) is reported here. The hydrolysis and condensation of TMOS was carried out in a solution of DMAc containing 5% LiCl, CaCl 2 or ZnCl 2 and the seven‐membered cyclic polyimide intermediate. The seven‐membered cyclic intermediates, precursors of polyimides, were derived from the low‐temperature polycondensation of dianhydrides [benzophenonetetracarboxylic dianhydride (BTDA), pyromellitic dianhydride (PMDA), and 4,4‐bis(hexafluoroisopropylidene)phthalic dianhydride (6FDA)] and di‐isocyanates [isophorone di‐isocyanate (IPDI), toluene di‐isocyanate (TDI), hexamethylene di‐isocyanate (HDI) and 4,4′‐diphenylmethane di‐isocyanate (MDI)]. These intermediates could readily be converted to the corresponding polyimides. Films were cast from the resulting mixtures and the solvent was gradually evaporated at 130 °C to result in the formation of clear, transparent, pale yellow or amber‐colored hybrid films in which the salts were dispersed at the molecular level. Pyrolysis of polyimide–silica gel hybrids at 600 °C gave mesoporous silica. Silica gel obtained from hybrids HPI‐8 (containing no salt) and HPI‐11 (containing ZnCl 2 ) had a pore radius (BJH method) of 2.9 nm, while that from hybrid HPI‐9 (containing LiCl) had a pore radius of 11.4 nm. The surface areas (BET method) obtained were 203 m 2 g −1 , 19 m 2 g −1 and 285 m 2 g −1 , while the pore volumes were 0.373 cm 3 g −1 , 0.158 cm 3 g −1 and 0.387 cm 3 g −1 , respectively, for samples obtained from hybrids HPI‐8, HPI‐9 and HPI‐11. © 1997 by John Wiley & Sons, Ltd.