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  • Temperature-ramping measurement of dye reorientation to probe molecular motion in polymer glasses.

Temperature-ramping measurement of dye reorientation to probe molecular motion in polymer glasses.

The Journal of chemical physics (2011-01-19)
Keewook Paeng, Hau-Nan Lee, Stephen F Swallen, M D Ediger
ABSTRACT

A temperature-ramping anisotropy measurement is introduced as an efficient way to study molecular motion in polymer glasses. For these experiments, fluorescent molecules were dispersed in the polymer glass and the reorientation of these dyes was used as a probe of segmental dynamics. For thick samples of polystyrene, poly (4-tert-butyl styrene), and poly(2-vinyl pyridine), temperature-ramping anisotropy measurements have a shape similar to differential scanning calorimetry measurements and nearly the same transition temperature. We present results using different fluorescent molecules and different temperature-ramping rates; such experiments show potential for accessing slow molecular motions considerably below T(g). Temperature-ramping anisotropy measurements were performed on freestanding poly (4-tert-butyl styrene) films of varying thicknesses. The anisotropy decay of a 22 nm film was shifted about 12 K lower in temperature as compared to a bulk sample.

MATERIALS
Product Number
Brand
Product Description

Supelco
Poly(2-vinylpyridine), analytical standard, average Mw 159,000 (Typical), average Mn 152,000 (Typical)
Supelco
Poly(2-vinylpyridine), analytical standard, average Mw 37,500 (Typical), average Mn 35,000 (Typical)