Free volume determination of azobenzene-PMMA copolymer by a pulsed low-energy positron lifetime beam with in-situ UV illumination
(2004) In Macromolecules 37(21). p.8035-8042- Abstract
- The free volume properties of a poly(methyl methacrylate)-azobenzene copolymer were for the first time directly probed by use of a low-energy positron lifetime beam with in-situ excitation capabilities, showing that the free volume cavity size was not appreciably influenced by photoisomerization and thermal isomerization in the temperature range 34-180 degreesC. lsomerization is therefore suggested to occur without any molecular rearrangement of the glassy polymer matrix, which would also account for the lack of any shift to shorter wavelengths for the photoisomerization occurring in a glassy polymer in comparison to a chloroform solution. A decrease in the thermal isomerization rate at room temperature caused by the glassy polymer is... (More)
- The free volume properties of a poly(methyl methacrylate)-azobenzene copolymer were for the first time directly probed by use of a low-energy positron lifetime beam with in-situ excitation capabilities, showing that the free volume cavity size was not appreciably influenced by photoisomerization and thermal isomerization in the temperature range 34-180 degreesC. lsomerization is therefore suggested to occur without any molecular rearrangement of the glassy polymer matrix, which would also account for the lack of any shift to shorter wavelengths for the photoisomerization occurring in a glassy polymer in comparison to a chloroform solution. A decrease in the thermal isomerization rate at room temperature caused by the glassy polymer is explained in terms of a model in which only a fraction of the azobenzene is free to isomerize. The cis-azobenzene was found to be an efficient inhibitor of positronium formation, which enabled measurements of thermal isomerization rates and changes in the steady-state concentration of cis-azobenzene for an illuminated sample as a function of temperature. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/139495
- author
- Algers, John LU ; Sperr, P ; Egger, W ; Liszkay, L ; Kogel, G ; de Baerdemaeker, J and Maurer, Frans LU
- organization
- publishing date
- 2004
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Macromolecules
- volume
- 37
- issue
- 21
- pages
- 8035 - 8042
- publisher
- The American Chemical Society (ACS)
- external identifiers
-
- wos:000224472500028
- scopus:7644222885
- ISSN
- 0024-9297
- DOI
- 10.1021/ma0486086
- language
- English
- LU publication?
- yes
- additional info
- The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Polymer and Materials Chemistry (LTH) (011001041)
- id
- 6d376c25-3c87-453b-b37c-a71862f3baae (old id 139495)
- date added to LUP
- 2016-04-01 11:40:55
- date last changed
- 2022-04-05 03:19:23
@article{6d376c25-3c87-453b-b37c-a71862f3baae,
abstract = {{The free volume properties of a poly(methyl methacrylate)-azobenzene copolymer were for the first time directly probed by use of a low-energy positron lifetime beam with in-situ excitation capabilities, showing that the free volume cavity size was not appreciably influenced by photoisomerization and thermal isomerization in the temperature range 34-180 degreesC. lsomerization is therefore suggested to occur without any molecular rearrangement of the glassy polymer matrix, which would also account for the lack of any shift to shorter wavelengths for the photoisomerization occurring in a glassy polymer in comparison to a chloroform solution. A decrease in the thermal isomerization rate at room temperature caused by the glassy polymer is explained in terms of a model in which only a fraction of the azobenzene is free to isomerize. The cis-azobenzene was found to be an efficient inhibitor of positronium formation, which enabled measurements of thermal isomerization rates and changes in the steady-state concentration of cis-azobenzene for an illuminated sample as a function of temperature.}},
author = {{Algers, John and Sperr, P and Egger, W and Liszkay, L and Kogel, G and de Baerdemaeker, J and Maurer, Frans}},
issn = {{0024-9297}},
language = {{eng}},
number = {{21}},
pages = {{8035--8042}},
publisher = {{The American Chemical Society (ACS)}},
series = {{Macromolecules}},
title = {{Free volume determination of azobenzene-PMMA copolymer by a pulsed low-energy positron lifetime beam with in-situ UV illumination}},
url = {{http://dx.doi.org/10.1021/ma0486086}},
doi = {{10.1021/ma0486086}},
volume = {{37}},
year = {{2004}},
}