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Glass Transition Temperature of Conjugated Polymers by Oscillatory Shear Rheometry

R. Xie ; Y. Lee ; M.P. Aplan ; N.J. Caggiano ; Christian Müller (Institutionen för kemi och kemiteknik, Polymerteknologi) ; R.H. Colby ; E.D. Gomez
Macromolecules (0024-9297). Vol. 50 (2017), 13, p. 5146-5154.
[Artikel, refereegranskad vetenskaplig]

The stiff backbones of conjugated polymers can lead to a rich phase behavior that includes both crystalline and liquid crystalline phases, making measurements of the glass transition challenging. In this work, the glass transitions of regioregular poly(3-hexylthiophene-2,5-diyl) (RR P3HT), regiorandom (RRa) P3HT, and poly((9,9-bis(2-octyl)-fluorene-2,7-diyl)-alt-(4,7-di(thiophene-2-yl)-2,1,3-benzothiadiazole)-5′,5″-diyl) (PFTBT) are probed by linear viscoelastic measurements as a function of molecular weight. We find two glass transition temperatures (T g 's) for both RR and RRa P3HT and one for PFTBT. The higher T g , T α , is associated with the backbone segmental motion and depends on the molecular weight, such that the Flory-Fox model yields T α = 22 and 6 °C in the long chain limit for RR and RRa P3HT, respectively. For RR P3HT, a different molecular weight dependence of T α is seen below M n = 14 kg/mol, suggesting this is the typical molecular weight of intercrystal tie chains. The lower T g (T αPE ≈ -100 °C) is associated with the side chains and is independent of molecular weight. RRa P3HT exhibits a lower T α and higher T αPE than RR P3HT, possibly due to a different degree of nanophase separation between the side chains and the backbones. In contrast, PFTBT only exhibits one T g above -120 °C, at 144 °C in the long chain limit.

Denna post skapades 2017-08-11. Senast ändrad 2017-08-11.
CPL Pubid: 251064


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Institutionen för kemi och kemiteknik, Polymerteknologi



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