Photothermal reaction kinetics and thermal desorption of diacetylene langmuir-blodgett films

✍ Scribed by L.A. Laxhuber; U. Scheunemann; H. Möhwald

• Publisher: Elsevier Science
• Year: 1986
• Tongue: English
• Weight: 543 KB
• Volume: 124
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(86)85076-x

✦ Synopsis

Photopolymerization and thermal changes in Langmuir-Blodgett films of diacetylene fatty acids are studied by reflection measurements. The technique is highly sensitive and allows investigation of the kinetics of changes in thickness and real and imaginary parts of the refractive index. In quantitative agreement with absorption and X-ray data, the reflectivity can be described by two consecutive photoreactions. The faster process involves an absorption, but no structural change, and the slower reaction an absorption change and an immediately coupled thickness increase by 6%. Polymerization removes a solid/fluid phase transition at 62°C for the unpolymerized fatty acid. Thermodesorption measurements demonstrate the increased thermostability by polymerization: Desorption temperatures are increased by 150°C corresponding to increases in binding energy of 9 kcal/mol.