Phase behavior of poly(9,9-di-n-hexyl-2,7-fluorene)

The Journal of Physical Chemistry. B
S H ChenS A Chen

Abstract

Here we report the phase behavior of poly(9,9-di-n-hexyl-2,7-fluorene) (PFH), which previously received little attention as compared to its homologues poly(9,9-di-n-octyl-2,7-fluorene) (PFO) and poly(9,9-di-(2'-ethylhexyl)-2,7-fluorene) (PFEH). By means of differential scanning calorimetry, X-ray diffraction, and electron microscopy, we show that there exist four different phases in PFH. The as-cast film is mainly composed of a mesomorphic beta phase with layer spacing of ca. 1.4 nm. This beta phase is inherently metastable and, upon heating above 175 degrees C, transforms into a crystalline (alpha) form that melts into a nematic (N) liquid above 250 degrees C. Upon stepwise cooling, the nematic melt crystallizes into the alpha phase first, followed by solid-solid transformation into another crystalline (alpha') form. Unit cell structure of the alpha form is monoclinic whereas that of the alpha' form is triclinic, but departures from strict orthogonality are slight (by ca. 6 degrees). These observations not only support our previous assignment of two crystalline forms (both orthorhombic in structure) in PFO but also provide insights to the crystalline nature of the polyfluorene series.

References

Jul 21, 2006·The Journal of Physical Chemistry. B·S H ChenS A Chen
Mar 2, 1998·Angewandte Chemie·Arno KraftAndrew B Holmes

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Citations

Apr 5, 2012·The Journal of Physical Chemistry. a·Oigres Daniel BernardinelliMelissa Fabíola Siqueira Pinto
Jan 30, 2008·Journal of Pharmaceutical Sciences·Harry G Brittain
Nov 18, 2014·The Journal of Physical Chemistry. B·Yonghong DengGao Liu
Aug 20, 2009·Chemistry : a European Journal·Robert AbbelAlbertus P H J Schenning
Jan 24, 2013·Advanced Materials·Matti Knaapila, Andrew P Monkman
Jul 23, 2008·Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics·M KnaapilaA P Monkman
Mar 19, 2013·Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics·M KnaapilaU Scherf
Jul 7, 2011·Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics·M KnaapilaA P Monkman
Jul 4, 2013·The Journal of Physical Chemistry. B·Chengfang LiuDonghang Yan

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