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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, John LU ; Suzuki, R; Ohdaira, T and Maurer, Frans LU (2004) In Macromolecules 37(11). p.4201-4210
Abstract
Density gradient widths at the polymer-vacuum surfaces of poly(methyl methacrylate), styrene-co-acrylonitrile, and styrene-co-maleic anhydride were quantified to 2, 5, and 4 rim, respectively, by use of a pulsed low-energy positron lifetime beam and to approximately 1.5 nm for all three polymers on the basis of theoretical predictions from pressure-volume-temperature (PVT) data, making use of the Cahn-Hilliard theory of inhomogeneous systems in conjunction with the Sanchez-Lacombe lattice fluid theory. Excellent agreement between the two methods was found for the homopolymer, whereas for the copolymers, the former method gave larger density gradient widths, a result attributed to the surface orientation of the less polar polymer segments,... (More)
Density gradient widths at the polymer-vacuum surfaces of poly(methyl methacrylate), styrene-co-acrylonitrile, and styrene-co-maleic anhydride were quantified to 2, 5, and 4 rim, respectively, by use of a pulsed low-energy positron lifetime beam and to approximately 1.5 nm for all three polymers on the basis of theoretical predictions from pressure-volume-temperature (PVT) data, making use of the Cahn-Hilliard theory of inhomogeneous systems in conjunction with the Sanchez-Lacombe lattice fluid theory. Excellent agreement between the two methods was found for the homopolymer, whereas for the copolymers, the former method gave larger density gradient widths, a result attributed to the surface orientation of the less polar polymer segments, which the theoretical predictions did not take into account. As has been previously proposed, the discrepancy between the depth ranges of the surface effects on density and the glass transition temperature (T-g) is suggested to result from a coupling between the dynamics of adjoining polymer segments, canceling a direct relationship between local density profile rho(z) and local T-g(z) as a function of distance z from the free surface. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Macromolecules
volume
37
issue
11
pages
4201 - 4210
publisher
The American Chemical Society
external identifiers
  • wos:000221688600037
  • scopus:2942592316
ISSN
0024-9297
DOI
10.1021/ma0359335
language
English
LU publication?
yes
id
a77fd69e-7954-49f8-b002-053dfd763e58 (old id 139521)
date added to LUP
2007-06-26 11:19:36
date last changed
2017-01-01 04:49:26
@article{a77fd69e-7954-49f8-b002-053dfd763e58,
  abstract     = {Density gradient widths at the polymer-vacuum surfaces of poly(methyl methacrylate), styrene-co-acrylonitrile, and styrene-co-maleic anhydride were quantified to 2, 5, and 4 rim, respectively, by use of a pulsed low-energy positron lifetime beam and to approximately 1.5 nm for all three polymers on the basis of theoretical predictions from pressure-volume-temperature (PVT) data, making use of the Cahn-Hilliard theory of inhomogeneous systems in conjunction with the Sanchez-Lacombe lattice fluid theory. Excellent agreement between the two methods was found for the homopolymer, whereas for the copolymers, the former method gave larger density gradient widths, a result attributed to the surface orientation of the less polar polymer segments, which the theoretical predictions did not take into account. As has been previously proposed, the discrepancy between the depth ranges of the surface effects on density and the glass transition temperature (T-g) is suggested to result from a coupling between the dynamics of adjoining polymer segments, canceling a direct relationship between local density profile rho(z) and local T-g(z) as a function of distance z from the free surface.},
  author       = {Algers, John and Suzuki, R and Ohdaira, T and Maurer, Frans},
  issn         = {0024-9297},
  language     = {eng},
  number       = {11},
  pages        = {4201--4210},
  publisher    = {The American Chemical Society},
  series       = {Macromolecules},
  title        = {Free volume and density gradients of amorphous polymer surfaces as determined by use of a pulsed low-energy positron lifetime beam and PVT data},
  url          = {http://dx.doi.org/10.1021/ma0359335},
  volume       = {37},
  year         = {2004},
}