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

TitleTemperature-ramping measurement of dye reorientation to probe molecular motion in polymer glasses
Publication TypeJournal Article
Year of Publication2011
AuthorsPaeng, K., H. N. Lee, S. F. Swallen, and M. D. Ediger
JournalJournal of Chemical Physics
Volume134
Start Page024901
ISBN Number0021-9606
Accession NumberWOS:000286471900075
KeywordsCONFINEMENT, DIELECTRIC-RELAXATION, DYNAMICS, MOBILITY, NANOCOMPOSITES, O-TERPHENYL, POLYSTYRENE, T-G, THIN-FILMS, TRANSITION TEMPERATURE
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.

DOI10.1063/1.3507255
Alternate JournalJ. Chem. Phys.