Adsorption of stereoregular poly(methyl methacrylates) on γ-alumina: Spectroscopic analysis

✍ Scribed by Yves Grohens; Michèle Auger; Robert E. Prud'homme; Jacques Schultz

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 228 KB
• Volume: 37
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/(sici)1099-0488(19991101)37:21<2985::aid-polb8>3.0.co;2-e

✦ Synopsis

Three poly(methyl methacrylates) (PMMA) with a racemic fraction ranging from 0.25 to 0.91 have been adsorbed from a chloroform solution on ␥-alumina and studied by diffuse reflectance infrared spectroscopy (DRIFT) and solid-state 13 C NMR spectroscopy. From DRIFT spectra, it is seen that the fraction of carbonyl groups bonded to the surface goes from 0.29 for s-PMMA to 0.41 for i-PMMA, but there is a larger amount of s-PMMA retained on the surface (at any given solution concentration). NMR spectroscopy indicates, from shifts of the methylene and ␣-methyl carbon peaks (due to the ␥-gauche effect), that the adsorption is accompanied by changes in conformation, with an increase in the number of trans conformers, particularly with i-PMMA. These results indicate that s-PMMA adsorbs on ␥-alumina in a brush-like configuration, with a relatively small number of groups attached to the surface, and tails and loops sticking out of the surface, whereas i-PMMA adsorbs in a sheet-like configuration, with a greater number of interacting groups. In both cases, the adsorption is accompanied with an increase in the number of trans conformers as compared to the bulk conformation.