Unperturbed dimensions of stereoregular polymers

Jenkins, Robert F.; Porter, Roger S.

doi:10.1007/3-540-10204-3_1

Cited by 14 publications

(1 citation statement)

References 82 publications

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“…The FL-TSCR behavior of PMMA S-36 is more questioning, because it is the worst packed polymer 2 and its chain stiffness is quite high compared with that of isotactic or syndiotactic PMMA. , Nevertheless the glass transition temperature T g is relatively high, about 105 °C. The full width at half-maximum of the Δ H i peak and glass transition broadness Δ T DSC are large compared with those of other samples.…”

Section: Discussionmentioning

confidence: 99%

Influence of Tacticity on the α Retardation Mode in Amorphous Poly(methyl methacrylate)

2000

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Thermally stimulated creep recovery (TSCR) experiments have been used to study the influence of tacticity on the R retardation process in amorphous poly(methyl methacrylate) (PMMA). The R retardation process associated with the glass transition is strongly dependent on tacticity. The highsensitivity TSCR-fractional loading (FL) method was used to extract the distributions of activation enthalpies ∆H and entropies ∆S of the R mechanical relaxation. ∆H increases with temperature and is maximum at the glass transition temperature T g. The maximum value and the full width at half-height of the activation enthalpy distribution are tacticity-dependent. Comparing experimental activation enthalpies with Starkweather's zero entropy prediction shows that the low-temperature tail of the R retardation process extends to 30 °C independent of tacticity. This result is attributed to the presence of isotriad sequences enhancing molecular mobility in this temperature range.

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Section: Discussionmentioning

confidence: 99%