Abstract
Polymers that have been cooled below their glass transition
temperature (Tg) are
amorphous, non-equilibrium solids. Because they are out of
equilibrium polymer glasses
experience a densification known as physical aging. Here, a thermal
reset protocol for
use in measuring the physical aging of polystyrene (PS, Tg=100
degrees C) in a multilayer
polymer film is discussed. Aging rates for single layer bulk films
of PS and
polycarbonate (PC, Tg=145 degrees C) supported on silicon
substrates were measured using
ellipsometry to test the ability of the protocol to accurately
measure physical aging in PS
while minimizing aging in PC. Bilayer polymer films were created
consisting of PC on
PS all supported on silicon. The aging rate of PS in the bilayer
system was measured
using ellipsometry and found to be consistent with single layer PS
values. This newly
established protocol may be used for probing the effects on PS of a
glassy interface with
PC.
Table of Contents
Contents
1 Introduction 1
1.1 Glass Transition 1
1.2 Physical Aging 3
1.3 Goal 3
2 Background 4
2.1 Permeability of Gas Separation Membranes 4
2.2 Differential Scanning Calorimetry 5
2.3 Forced Assembly of Nanolayers 6
2.4 Glassy-glassy Interfaces in Polymer Systems 7
2.5 Ellipsometry 10
2.6 Tg and Aging of PS 15
3 Investigating the Physical Aging Behavior of PC/PS Bilayer Films
by
Ellipsometry 19
3.1 Procedure 19
3.1.1 Production of Single Layer PS and PC films 20
3.1.2 Production of the Bilayer System 20
3.1.3 Physical Aging 21
3.2 Thermal Reset Protocol 21
3.3 Bilayer Aging Measurements 24
4 Conclusions and Future Work 26
Bibliography 28
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