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Oligomeric Alkoxysilanes with Cagelike Hybrids as Cores: Designed Precursors of Nanohybrid Materials
Author(s) -
Kuge Hideki,
Hagiwara Yoshiaki,
Shimojima Atsushi,
Kuroda Kazuyuki
Publication year - 2008
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.200700242
Subject(s) - silsesquioxane , alkoxy group , siloxane , condensation polymer , microporous material , silylation , sol gel , hybrid material , copolymer , materials science , amphiphile , polymer chemistry , trimer , hydrolysis , polymerization , chemical engineering , ring opening polymerization , chemistry , catalysis , organic chemistry , nanotechnology , polymer , alkyl , dimer , engineering
Well‐defined alkoxysilane oligomers containing a cagelike carbosiloxane core were synthesized and used as novel building blocks for the formation of siloxane‐based hybrid networks. These oligomers were synthesized from the cagelike trimer derived from bis(triethoxysilyl)methane by silylation with mono‐, di‐, and triethoxychlorosilanes ((EtO) n Me 3− n SiCl, n =1, 2, and 3). Hybrid xerogels were prepared by hydrolysis and polycondensation of these oligomers under acidic conditions. The structures of the products varied depending on the number of alkoxy groups ( n ). When n =2 and 3, microporous xerogels (BET surface areas of 820 and 510 m 2 g −1 , respectively) were obtained, whereas a nonporous xerogel was obtained when n =1. 29 Si NMR spectroscopic analysis suggested that partial rearrangement of the siloxane networks, which accompanied the cleavage of the Si–O–Si linkages, occurred during the polycondensation processes. By using an amphiphilic triblock copolymer surfactant as a structure‐directing agent, hybrid thin films with a 2D hexagonal mesostructure were obtained when n =2 and 3. These results provide important insight into the rational synthesis of molecularly designed hybrid materials by sol–gel chemistry.