Highly ordered "defect-free" self-assembled hybrid films with a tetragonal mesostructure.
One-pot self-assembled hybrid films were synthesized by the cohydrolysis of methyltriethoxysilane and tetraethoxysilane and deposited via dip-coating. The films show a high "defect-free" mesophase organization that extends throughout the film thickness and for domains of a micrometer scale, as shown by scanning transmission electron microscopy. We have defined these films defect-free to describe the high degree of order that is achieved without defects in the pore organization, such as dislocations of pores or stacking faults. A novel mesophase, which is tetragonal I4/mmm (space group), is observed in the films. This phase evolves but retains the same symmetry throughout a wide range of temperatures of calcination. The thermal stability and the structural changes as a function of the calcination temperature have been studied by small-angle X-ray scattering, scanning transmission electron microscopy, and Fourier transform infrared spectroscopy. In situ Fourier transform infrared spectroscopy employing synchrotron radiation has been used to study the kinetics of film formation during the deposition. The experiments have shown that the slower kinetics of silica species can explain the high degree of organization of the mesostructure.
Falcaro
Paolo
P
Dipartimento di Ingegneria Meccanica, Settore Materiali, Università di Padova, Via Marzolo 9, 35131 Padova, Italy.
Costacurta
Stefano
S
Mattei
Giovanni
G
Amenitsch
Heinz
H
Marcelli
Augusto
A
Guidi
Mariangela Cestelli
MC
Piccinini
Massimo
M
Nucara
Alessandro
A
Malfatti
Luca
L
Kidchob
Tongjit
T
Innocenzi
Plinio
P