Polarized optical absorption spectroscopy, NEXAFS, and GIXRD measurements of chain alignment in polyfluorene thin films
(2008) In Macromolecules 41(17). p.6463-6472- Abstract
- The uniaxial chain alignment of low molecular weight poly(9,9-bis(ethylhexyl)fluorene-2,7-diyl) (PF2/6) in thin films cast atop rubbed polyimide templates is characterized by polarized optical absorption spectroscopy, carbon K near-edge X-ray absorption fine structure spectroscopy (NEXAFS), and grazing incidence X-ray diffraction (GIXRD) in response to thermal annealing and increasing film thickness (ca. 15-150 nm). The highest overall levels of uniaxial alignment are obtained in the thinnest PF2/6 films. However, the orientation of chains at the top surface after thermal annealing is nearly thickness independent despite a large drop in the maximum optical dichroic ratio as the film thickness increases. The kinetics of chain alignment on... (More)
- The uniaxial chain alignment of low molecular weight poly(9,9-bis(ethylhexyl)fluorene-2,7-diyl) (PF2/6) in thin films cast atop rubbed polyimide templates is characterized by polarized optical absorption spectroscopy, carbon K near-edge X-ray absorption fine structure spectroscopy (NEXAFS), and grazing incidence X-ray diffraction (GIXRD) in response to thermal annealing and increasing film thickness (ca. 15-150 nm). The highest overall levels of uniaxial alignment are obtained in the thinnest PF2/6 films. However, the orientation of chains at the top surface after thermal annealing is nearly thickness independent despite a large drop in the maximum optical dichroic ratio as the film thickness increases. The kinetics of chain alignment on heating are strongly film thickness dependent and only weakly correlated with a crossover to a nematic liquid crystal state. All told these data support a structural model in which there is a graded morphology such that the top and bottom surfaces exhibit appreciable planar, uniaxial alignment while the film interior includes a greater proportion of nomplanar (i.e., tilted) chains after thermal cycling. These inhomogeneities are likely to influence technologically important optical and transport properties. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/1247709
- author
- Cheun, H. ; Liu, X. ; Himpsel, F. J. ; Knaapila, Matti LU ; Scherf, U. ; Torkkeli, M. and Winokur, A. J.
- organization
- publishing date
- 2008
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Macromolecules
- volume
- 41
- issue
- 17
- pages
- 6463 - 6472
- publisher
- The American Chemical Society (ACS)
- external identifiers
-
- wos:000258909000029
- scopus:52449104616
- ISSN
- 0024-9297
- DOI
- 10.1021/ma702579r
- language
- English
- LU publication?
- yes
- id
- 8602cc70-982d-4ae0-ad07-4e698916bdae (old id 1247709)
- date added to LUP
- 2016-04-01 11:37:07
- date last changed
- 2022-03-12 22:11:59
@article{8602cc70-982d-4ae0-ad07-4e698916bdae,
abstract = {{The uniaxial chain alignment of low molecular weight poly(9,9-bis(ethylhexyl)fluorene-2,7-diyl) (PF2/6) in thin films cast atop rubbed polyimide templates is characterized by polarized optical absorption spectroscopy, carbon K near-edge X-ray absorption fine structure spectroscopy (NEXAFS), and grazing incidence X-ray diffraction (GIXRD) in response to thermal annealing and increasing film thickness (ca. 15-150 nm). The highest overall levels of uniaxial alignment are obtained in the thinnest PF2/6 films. However, the orientation of chains at the top surface after thermal annealing is nearly thickness independent despite a large drop in the maximum optical dichroic ratio as the film thickness increases. The kinetics of chain alignment on heating are strongly film thickness dependent and only weakly correlated with a crossover to a nematic liquid crystal state. All told these data support a structural model in which there is a graded morphology such that the top and bottom surfaces exhibit appreciable planar, uniaxial alignment while the film interior includes a greater proportion of nomplanar (i.e., tilted) chains after thermal cycling. These inhomogeneities are likely to influence technologically important optical and transport properties.}},
author = {{Cheun, H. and Liu, X. and Himpsel, F. J. and Knaapila, Matti and Scherf, U. and Torkkeli, M. and Winokur, A. J.}},
issn = {{0024-9297}},
language = {{eng}},
number = {{17}},
pages = {{6463--6472}},
publisher = {{The American Chemical Society (ACS)}},
series = {{Macromolecules}},
title = {{Polarized optical absorption spectroscopy, NEXAFS, and GIXRD measurements of chain alignment in polyfluorene thin films}},
url = {{http://dx.doi.org/10.1021/ma702579r}},
doi = {{10.1021/ma702579r}},
volume = {{41}},
year = {{2008}},
}