Free Volume Depth Profiling at Polymer Surfaces and Interfaces
(2004)- Abstract
- Pulsed low energy positron beams provide a unique and non-destructive tool to depth probe the free volume of polymers at surfaces and interfaces. Since the employment of low energy positron beams in polymer research is an emerging technique, some focus in this thesis has been on extracting methods and equations needed to interpret the experimental data. The polymers chosen for this study were selected on the basis of having previously well characterized free volume properties. This enabled interpretation of the positron beam data in more general quantities, thus permitting the results to be compared with other techniques and theoretical considerations of polymer surfaces and interfaces. The median positron implantation depth and the... (More)
- Pulsed low energy positron beams provide a unique and non-destructive tool to depth probe the free volume of polymers at surfaces and interfaces. Since the employment of low energy positron beams in polymer research is an emerging technique, some focus in this thesis has been on extracting methods and equations needed to interpret the experimental data. The polymers chosen for this study were selected on the basis of having previously well characterized free volume properties. This enabled interpretation of the positron beam data in more general quantities, thus permitting the results to be compared with other techniques and theoretical considerations of polymer surfaces and interfaces. The median positron implantation depth and the implantation depth distribution as a function of implantation energy have been studied in some detail. It was shown that the implantation characteristics are independent of the structure of the materials, and that the median implantation depth for the studied polymers, as well as those of some previously studied metals, can be described with the same equation. Furthermore, the free surfaces of polystyrene (PS), polymethyl methacrylate (PMMA), styrene-co-acrylonitrile (SAN) and styrene-co-maleic anhydride (SMA) were studied by measurements in the low implantation energy range. Linear density gradients could be fitted to the experimental data, yielding gradient widths in the order of a few nanometers. This was in good or reasonable agreement with theoretically derived density gradients. The discrepancy with the theory found for the copolymers SAN and SMA was suggested to arise from surface orientation driven by the difference in polarity between the molecular constituents. The free volume at a PMMA-PS interface was studied. By the preparation of samples with the interface located only 25 nm from the free surface, the sensitivity of the experimental data to properties of interface region was greatly increased in relation to previous investigations. A reduction of the free volume was found in the PMMA in the 20 nm region closest to the PS surface. This finding suggests that the PS surface constitutes a relatively attractive environment for the PMMA. By guiding UV-light into the positron beam, various measurements relevant for photo-responsive polymers were enabled. Free volume determination of an azobenzene-PMMA copolymer during isomerization was carried out at various temperatures, showing that the isomerization did not influence the free volume. The excited cis-azobenzene was however found to be an inhibitor for positronium annihilation, which enabled the isomerization kinetics of azobenzene to be probed with positrons. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/467502
- author
- Algers, John LU
- supervisor
- opponent
-
- Dr Kobayashi, Yoshinori
- organization
- publishing date
- 2004
- type
- Thesis
- publication status
- published
- subject
- keywords
- biopolymers, Polymerteknik, Polymer technology, polymer interfaces, polymer surfaces, positron lifetime, free volume
- pages
- 146 pages
- publisher
- Birgitta Ryd, Polymer Science & Engineering, Center for Chemistry and Chemical Engineering, Lund,
- defense location
- Lecture Hall K:C, Center for Chemistry and Chemical Engineering, Lund Institute of Technology.
- defense date
- 2004-11-12 13:15:00
- ISBN
- 91-7422-063-2
- language
- English
- LU publication?
- yes
- additional info
- Article: Median implantation depth and implantation profile of 3-18 keV positrons in amorphous polymers.Algers, J.; Sperr, P.; Egger, W.; Kögel, G.; Maurer, F. H. J.Phys. Rev. B 2003, 67, 125404. Article: Free volume and density gradients of amorphous polymer surfaces as determined by use of a pulsed low-energy positron lifetime beam and PVT data. Algers, J.; Suzuki, R.; Ohdaira, T.;Maurer, F. H. J.Macromolecules 2004, 37, 4201-4210. Article: Characterization of free volume and density gradients of polystyrene surfaces by low-energy positron lifetime measurements.Algers, J.; Suzuki, R.; Ohdaira, T.;Maurer, F. H. J.Polymer 2004, 45, 4533-4539. Article: Free volume depth profiling at a PS-PMMA interface by use of a pulsed low-energy positron lifetime beam.Algers, J.; Sperr, P.; Egger, W.; Liszkay, L.; Kögel, G.; Maurer, F. H. J.(Manuscript to be submitted) Article: Free volume determination of azobenzene-PMMA copolymer by a pulsed low-energy positron beam with in situ UV-illumination.Algers, J.; Sperr, P.; Egger, W.; Liszkay, L.; Kögel, G.; de Baerdemaeker, J.; Maurer, F. H. J.Macromolecules 2004 (in press) 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
- a81f01ce-c966-4501-b25a-a546f53a808f (old id 467502)
- date added to LUP
- 2016-04-04 10:21:20
- date last changed
- 2018-11-21 20:58:17
@phdthesis{a81f01ce-c966-4501-b25a-a546f53a808f,
abstract = {{Pulsed low energy positron beams provide a unique and non-destructive tool to depth probe the free volume of polymers at surfaces and interfaces. Since the employment of low energy positron beams in polymer research is an emerging technique, some focus in this thesis has been on extracting methods and equations needed to interpret the experimental data. The polymers chosen for this study were selected on the basis of having previously well characterized free volume properties. This enabled interpretation of the positron beam data in more general quantities, thus permitting the results to be compared with other techniques and theoretical considerations of polymer surfaces and interfaces. The median positron implantation depth and the implantation depth distribution as a function of implantation energy have been studied in some detail. It was shown that the implantation characteristics are independent of the structure of the materials, and that the median implantation depth for the studied polymers, as well as those of some previously studied metals, can be described with the same equation. Furthermore, the free surfaces of polystyrene (PS), polymethyl methacrylate (PMMA), styrene-co-acrylonitrile (SAN) and styrene-co-maleic anhydride (SMA) were studied by measurements in the low implantation energy range. Linear density gradients could be fitted to the experimental data, yielding gradient widths in the order of a few nanometers. This was in good or reasonable agreement with theoretically derived density gradients. The discrepancy with the theory found for the copolymers SAN and SMA was suggested to arise from surface orientation driven by the difference in polarity between the molecular constituents. The free volume at a PMMA-PS interface was studied. By the preparation of samples with the interface located only 25 nm from the free surface, the sensitivity of the experimental data to properties of interface region was greatly increased in relation to previous investigations. A reduction of the free volume was found in the PMMA in the 20 nm region closest to the PS surface. This finding suggests that the PS surface constitutes a relatively attractive environment for the PMMA. By guiding UV-light into the positron beam, various measurements relevant for photo-responsive polymers were enabled. Free volume determination of an azobenzene-PMMA copolymer during isomerization was carried out at various temperatures, showing that the isomerization did not influence the free volume. The excited cis-azobenzene was however found to be an inhibitor for positronium annihilation, which enabled the isomerization kinetics of azobenzene to be probed with positrons.}},
author = {{Algers, John}},
isbn = {{91-7422-063-2}},
keywords = {{biopolymers; Polymerteknik; Polymer technology; polymer interfaces; polymer surfaces; positron lifetime; free volume}},
language = {{eng}},
publisher = {{Birgitta Ryd, Polymer Science & Engineering, Center for Chemistry and Chemical Engineering, Lund,}},
school = {{Lund University}},
title = {{Free Volume Depth Profiling at Polymer Surfaces and Interfaces}},
year = {{2004}},
}