Publication Type Journal Article
Title New contributions from thermal and dielectric techniques to the understanding of the dynamic properties of medium to long chain poly (propylene glycols)
Authors H. P. Diogo J. J. Moura-Ramos
Groups BioMol
Year 2021
Month June
Volume 61
Number 6
Pages 1638-1649
Abstract The molecular mobility of poly (propylene glycols) with molecular weights between 2000 and 18,200 g mol(-1) was studied in the amorphous solid state, in the region of the glass transition and in the rubbery state; the experimental techniques used were differential scanning calorimetry (DSC) and thermally stimulated depolarization currents (TSDC). It was found that the glass transition temperature increases slightly with MW and tends to a limit value: T-gDSC = -67 degrees C, T-gTSDC = -73 degrees C. The different types of molecular mobility were analyzed: below T-g the secondary relaxations, and above this temperature the normal mode, were characterized in detail using TSDC; in the glassy transformation region, around T-g, the main relaxation was analyzed by both DSC and TSDC. It was found the dynamic fragility, m, behaves as independent of the molecular weight in the studied range: m(DSC) = 74 and m(TSDC) = 92. The TSDC results also show that, without influencing the kinetics of the segmental relaxation, the increase in molecular weight slows down the chain relaxation.
Book Title
ISSN 0032-3888
EISSN 1548-2634
Conference Name
Bibtex ID ISI:000629318000001
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