Phase transitions in Langmuir-Blodgett films of cadmium stearate: Grazing incidence X-ray diffraction studies

Peng, JB, Foran, GJ, Barnes, GT and Gentle, IR (1997) Phase transitions in Langmuir-Blodgett films of cadmium stearate: Grazing incidence X-ray diffraction studies. Langmuir, 13 6: 1602-1606. doi:10.1021/la9608268


Author Peng, JB
Foran, GJ
Barnes, GT
Gentle, IR
Title Phase transitions in Langmuir-Blodgett films of cadmium stearate: Grazing incidence X-ray diffraction studies
Journal name Langmuir   Check publisher's open access policy
ISSN 0743-7463
Publication date 1997-03-01
Year available 1997
Sub-type Article (original research)
DOI 10.1021/la9608268
Open Access Status DOI
Volume 13
Issue 6
Start page 1602
End page 1606
Total pages 5
Place of publication WASHINGTON
Publisher AMER CHEMICAL SOC
Language eng
Abstract Variations in the structure of multilayer Langmuir-Blodgett (LB) films of cadmium stearate with temperature have been monitored by grazing incidence synchrotron X-ray diffraction. At room temperature the film structure comprises a centered rectangular unit cell in the plane of the substrate with the hydrocarbon chains normal to the substrate surface. As the temperature increases up to 90 degrees C, the diffraction pattern due to this in-plane structure becomes diffuse and the intensity decreases. Changes in the Q-values of the in-plane spots indicate an anisotropic expansion of the unit cell. At around 100 degrees C the film undergoes a phase transition from a layered three-dimensional crystalline structure to an array of rod structures packed hexagonally. The rods are oriented parallel to the surface of the film. The core of each rod is 6.7 Angstrom in diameter and appears to be composed of cadmium cations and the carboxylate groups of the fatty acid chains. The aliphatic chains are randomly arranged around these rods. The rod structure is retained on cooling, but the observed correlation length is reduced.
Keyword Multilayers
Monolayers
Soaps
Raman
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collection: ResearcherID Downloads - Archived
 
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