Effect of Adjacent Rubbery Layers on the Physical Aging of Polymer Glasses Open Access

Abstract

Upon cooling through their glass transition temperature (Tg), polymers form non-equilibrium solids and subsequently undergo physical aging. I developed a method of measuring the physical aging rate of thin polystyrene (PS, Tg = 373 K) films atop poly(n-butyl methacrylate) (PnBMA, Tg = 299 K) layers at aging temperatures between the two polymer Tgs in order to investigate the effect of a glassy/rubbery interface on structural relaxation in confined glassy polymer systems. To accomplish this, I devised a new ellipsometry protocol and data analysis method, expanding off a previous method developed in the Roth laboratory for characterizing the physical aging rate of single layer films. In order to interpret my results, I also used fluorescence spectroscopy to measure the Tg of the PS layer in the bilayer morphology. Despite very large reductions in PS Tg in the bilayer system no reductions in physical aging rate are observed, in strong contrast to results from single layers, suggesting the presence of some undefined mechanism stemming from the glassy/rubbery interface.

Table of Contents

Introduction 1
Polymers and Advanced Applications 1 Glassy Behavior and Physical Aging 1 Goal of Thesis 3 Background 4 Measurement of Tg- using Fluorescence Spectroscopy 4

Measurement of Physical Aging by Ellipsometry 6

Polymer Glasses in Confinement 9 Physical Aging in Glassy/Rubbery Systems 14

Materials and Methods 17

Results and Discussion 20

Tg of Bilayer Films as Measured by Fluorescence 20

Method of Physical Aging Rate Measurement in Bilayer Films 21

Physical Aging Rate of Bilayer Films with Varying Layer Thickness 28

Bilayer Aging Rate vs. Aging Temperature 34

Conclusions and Future Directions 36 References 38

About this Honors Thesis

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School	Emory College
Department	Physics
Degree	BS
Submission	Honors Thesis
Language	English
Research Field	Engineering, Materials Science Chemistry, Polymer
Keyword	Polymer Physical Aging Rubbery Interfaces Glass
Committee Chair / Thesis Advisor	Roth, Connie, Emory University
Committee Members	Weeks, Eric, Emory University McCormick, Michael, Emory University

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