Concentration-dependent formation mechanisms in mesophase silica-surfactant films
Brennan, Tessa ; Hughes, Arwel V. ; Roser, Stephen J. ; Mann, Stephen and Edler, Karen J. LU
(2002)
In Langmuir
18(25).
p.9838-9844
- Abstract
The development of surfactant-templated mesoporous films grown at the air/water interface was investigated using specular and off-specular X-ray reflectivity techniques. The samples were prepared in acidic conditions using cetyltrimethylammonium bromide (CTABr, 0.075 M) and different concentrations (0.27-0.88 M) of tetramethyloxysilane (TMOS). At CTABr/TMOS molar ratio between 0.277 and 0.093, the final films exhibited at least three orders of diffraction, corresponding to a real space repeat distance of 46 Å. This long-range order was not observed when the TMOS content was increased to 0.88 M at constant CTABr concentration. In each case, the induction period to film formation was monitored using diffuse X-ray scattering. The intensity... (More)
The development of surfactant-templated mesoporous films grown at the air/water interface was investigated using specular and off-specular X-ray reflectivity techniques. The samples were prepared in acidic conditions using cetyltrimethylammonium bromide (CTABr, 0.075 M) and different concentrations (0.27-0.88 M) of tetramethyloxysilane (TMOS). At CTABr/TMOS molar ratio between 0.277 and 0.093, the final films exhibited at least three orders of diffraction, corresponding to a real space repeat distance of 46 Å. This long-range order was not observed when the TMOS content was increased to 0.88 M at constant CTABr concentration. In each case, the induction period to film formation was monitored using diffuse X-ray scattering. The intensity of the specular reflectivity peak, first and second-order diffraction peaks, and Yoneda wing were recorded as a function of time. The reflected intensity of the specular peak oscillated during the lengthy induction period, indicating that at some concentrations the films nucleate at the surface through a phase separation mechanism followed by growth of ordered arrays. This oscillation has been modeled as a surface layer having increasing thickness and roughness with time. The evolution of the first-order diffraction peak displays different characteristics depending on the TMOS content. For the shortest induction times (corresponding to a molar ratio of 0.139) the film formation mechanism appears to be bulk driven, but for longer development periods the film forms through assembly of ordered arrays at the surface.
(Less)
- author
- Brennan, Tessa
; Hughes, Arwel V.
; Roser, Stephen J.
; Mann, Stephen
and Edler, Karen J.
LU
- publishing date
- 2002-12-10
- type
- Contribution to journal
- publication status
- published
- in
- Langmuir
- volume
- 18
- issue
- 25
- pages
- 7 pages
- publisher
- The American Chemical Society (ACS)
- external identifiers
-
- scopus:0037059230
- ISSN
- 0743-7463
- DOI
- 10.1021/la026192o
- language
- English
- LU publication?
- no
- id
- 670d77a3-2249-47bf-ac1b-9804f6a3f9ca
- date added to LUP
- 2023-05-04 18:38:27
- date last changed
- 2023-06-13 12:26:06
@article{670d77a3-2249-47bf-ac1b-9804f6a3f9ca,
abstract = {{<p>The development of surfactant-templated mesoporous films grown at the air/water interface was investigated using specular and off-specular X-ray reflectivity techniques. The samples were prepared in acidic conditions using cetyltrimethylammonium bromide (CTABr, 0.075 M) and different concentrations (0.27-0.88 M) of tetramethyloxysilane (TMOS). At CTABr/TMOS molar ratio between 0.277 and 0.093, the final films exhibited at least three orders of diffraction, corresponding to a real space repeat distance of 46 Å. This long-range order was not observed when the TMOS content was increased to 0.88 M at constant CTABr concentration. In each case, the induction period to film formation was monitored using diffuse X-ray scattering. The intensity of the specular reflectivity peak, first and second-order diffraction peaks, and Yoneda wing were recorded as a function of time. The reflected intensity of the specular peak oscillated during the lengthy induction period, indicating that at some concentrations the films nucleate at the surface through a phase separation mechanism followed by growth of ordered arrays. This oscillation has been modeled as a surface layer having increasing thickness and roughness with time. The evolution of the first-order diffraction peak displays different characteristics depending on the TMOS content. For the shortest induction times (corresponding to a molar ratio of 0.139) the film formation mechanism appears to be bulk driven, but for longer development periods the film forms through assembly of ordered arrays at the surface.</p>}},
author = {{Brennan, Tessa and Hughes, Arwel V. and Roser, Stephen J. and Mann, Stephen and Edler, Karen J.}},
issn = {{0743-7463}},
language = {{eng}},
month = {{12}},
number = {{25}},
pages = {{9838--9844}},
publisher = {{The American Chemical Society (ACS)}},
series = {{Langmuir}},
title = {{Concentration-dependent formation mechanisms in mesophase silica-surfactant films}},
url = {{http://dx.doi.org/10.1021/la026192o}},
doi = {{10.1021/la026192o}},
volume = {{18}},
year = {{2002}},
}