Direct Detection of High Mobility around Chain Ends of Poly(methyl methacrylate) by the Spin-Labeling
| Autor: | Masahiro Sakai, Katsuhiro Yamamoto, Seiji Makita, Masato Sakaguchi, Shigetaka Shimada, Yohei Miwa |
|---|---|
| Rok vydání: | 2005 |
| Předmět: |
chemistry.chemical_classification
Polymers and Plastics Chemistry Atom-transfer radical-polymerization Organic Chemistry Polymer Poly(methyl methacrylate) law.invention Inorganic Chemistry Crystallography End-group chemistry.chemical_compound law visual_art Polymer chemistry Materials Chemistry visual_art.visual_art_medium Methyl methacrylate Glass transition Electron paramagnetic resonance Spin label |
| Zdroj: | Macromolecules. 38:832-838 |
| ISSN: | 1520-5835 0024-9297 |
| DOI: | 10.1021/ma048287y |
| Popis: | Effects of chain ends on the dynamics of atactic poly(methyl methacrylate) (PMMA) was studied by the spin-label technique. PMMA's with well-defined molecular weights were synthesized by atom transfer radical polymerization and selectively labeled at the end or inside sites of the chain with a stable nitroxide radical. The WLF treatment demonstrated that a transition temperature, T5.0mT, at which an extreme separation width was 5.0 mT, reflected the glass transition observed at a frequency of electron spin resonance (ESR). The T5.0mT of the PMMA labeled at the chain end (T5.0mT,e) was ca. 8 K lower than that of the PMMA labeled at the inside sites (T5.0mT,i). From the comparison of some polymers, the difference between the T5.0mT,i and T5.0mT,e of a rigid polymer was found to be larger than that of a flexible polymer. The T5.0mT,i and T5.0mT,e decreased with a decrease in the molecular weight as well as a glass transition temperature determined by calorimetric measurements. This result supports that the T5... |
| Databáze: | OpenAIRE |
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