Influence of tacticity on the retardation mode associated with Tg in PMMA

The anelastic properties of PMMA in the temperature range of the main retardation mode are strongly dependent upon tacticity. The thermally stimulated creep (TSCr) technique was used to analyse the distribution function of retardation times. A series of PMMA, with various tacticities, synthesized by living polymerization, were investigated. One of the most important findings was the observation of a sub-mode, at 150 degrees C, with a magnitude increasing with syndiotactic triads. The existence of physical interactions might explain this behaviour. On the low-temperature tail of the alpha retardation mode, a sub-mode was observed at 60 degrees C: it was associated with remaining isotactic triads.