Proton NMR investigation of the local dynamics of PEO in PEO/PMMA blends

✍ Scribed by C. Lartigue; A. Guillermo; J. P. Cohen–Addad

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 247 KB
• Volume: 35
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/(sici)1099-0488(199705)35:7<1095::aid-polb8>3.0.co;2-v

✦ Synopsis

Longitudinal relaxation of proton magnetisation was used to characterize the molecular motions of PEO chains in compatible PEO (hydrogenated)/PMMA (deuterated) blends. Both the temperature and the PEO concentration, f, were varied. A maximum in the spin-lattice relaxation rate was observed and its properties were analyzed as a function of f. For f °0.50, the maximum is observed below the glass transition temperature of the blend; this shows that PEO chains dispersed in a matrix of PMMA remain highly mobile on a local scale even below T g (f). A frequency-temperature correspondence procedure, applied to the measurements performed at two Larmor frequencies, 32 and 60 MHz, leads to a characteristic correlation time for PEO molecular motions. Its temperature dependence obeys a WLF free volume relation above the glass transition of the blends. The PEO free volume fraction and its thermal expansion are strongly reduced by the presence of the PMMA chains.