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Thermal isomerization of azo-benzene in PMMA probed by a pulsed low-energy positron beam

Algers, John LU ; Skeppstedt, V; Sperr, P; Egger, W and Maurer, Frans LU (2004) Positron Annihilation: Proceedings of the 13th International Conference on Positron Annihilation, ICPA-13 In Materials Science Forum 445-446. p.262-264
Abstract
Polymers containing the Azo-benzene group have attracted attention due to anticipated uses such as materials for data storage, membranes with controllable permeability and materials with changeable solubility [1,2]. These expectations are due to the change in shape and dipole moment of the Azo-compound when excited by photo isomerization from the trans-state to the cis-state by UV light of ca 360 nm. Films of copolymers of poly-methyl methacrylate (PMMA) containing 8 wt-% Azo-benzene were photo isomerized with a UV lamp and then measured as a function of time in a lowenergy positron beam. The observed changes in the lifetime parameters as a function of time were in agreement with the thermal isomerization (decay) of the cis-isomer as... (More)
Polymers containing the Azo-benzene group have attracted attention due to anticipated uses such as materials for data storage, membranes with controllable permeability and materials with changeable solubility [1,2]. These expectations are due to the change in shape and dipole moment of the Azo-compound when excited by photo isomerization from the trans-state to the cis-state by UV light of ca 360 nm. Films of copolymers of poly-methyl methacrylate (PMMA) containing 8 wt-% Azo-benzene were photo isomerized with a UV lamp and then measured as a function of time in a lowenergy positron beam. The observed changes in the lifetime parameters as a function of time were in agreement with the thermal isomerization (decay) of the cis-isomer as measured by conventional UV spectroscopy. The results show that positron lifetime spectra at low energy are sensitive for the cis-trans isomerization of the Azo-compound, suggesting trapping and annihilation of positrons at free volume sites around the Azo-benzene groups. (Less)
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author
organization
publishing date
type
Chapter in Book/Report/Conference proceeding
publication status
published
subject
in
Materials Science Forum
volume
445-446
pages
262 - 264
publisher
Trans Tech Publications Ltd
conference name
Positron Annihilation: Proceedings of the 13th International Conference on Positron Annihilation, ICPA-13
external identifiers
  • wos:000189406800076
  • scopus:3142781608
ISSN
0255-5476
language
English
LU publication?
yes
id
afc5302f-ed40-40ee-a514-91f761d23877 (old id 139537)
date added to LUP
2007-11-26 15:55:16
date last changed
2017-01-01 06:57:12
@inproceedings{afc5302f-ed40-40ee-a514-91f761d23877,
  abstract     = {Polymers containing the Azo-benzene group have attracted attention due to anticipated uses such as materials for data storage, membranes with controllable permeability and materials with changeable solubility [1,2]. These expectations are due to the change in shape and dipole moment of the Azo-compound when excited by photo isomerization from the trans-state to the cis-state by UV light of ca 360 nm. Films of copolymers of poly-methyl methacrylate (PMMA) containing 8 wt-% Azo-benzene were photo isomerized with a UV lamp and then measured as a function of time in a lowenergy positron beam. The observed changes in the lifetime parameters as a function of time were in agreement with the thermal isomerization (decay) of the cis-isomer as measured by conventional UV spectroscopy. The results show that positron lifetime spectra at low energy are sensitive for the cis-trans isomerization of the Azo-compound, suggesting trapping and annihilation of positrons at free volume sites around the Azo-benzene groups.},
  author       = {Algers, John and Skeppstedt, V and Sperr, P and Egger, W and Maurer, Frans},
  booktitle    = {Materials Science Forum},
  issn         = {0255-5476},
  language     = {eng},
  pages        = {262--264},
  publisher    = {Trans Tech Publications Ltd},
  title        = {Thermal isomerization of azo-benzene in PMMA probed by a pulsed low-energy positron beam},
  volume       = {445-446},
  year         = {2004},
}