Advisor(s)

Nathan E. (Nathan Eli) Israeloff (1961-)

Contributor(s)

Jeffrey B. Sokoloff, Mark C. Williams

Date of Award

2008

Date Accepted

8-2008

Degree Grantor

Northeastern University

Degree Level

Ph.D.

Degree Name

Doctor of Philosophy

Department or Academic Unit

College of Arts and Sciences. Department of Physics.

Keywords

Physics, Condensed matter, Glassy polymer, Glass transition, Fluctuation dissipation relation, Aging phenomenon, Scaling behavior

Subject Categories

Polymers--Thermal properties, Glass transition temperature

Disciplines

Physics

Abstract

The goal of this work is to study the validity of the fluctuation dissipation relation (FDR) during aging in a glassy polymer and in general glassy dynamics, through probing aging dynamics, in thin films of polyvinyl acetate (PVAc). We use a rapid quench process by applying local radiation heating to a thin layer capacitor. The time evolution of polarization noise and dielectric susceptibility are analyzed in the frequency range 0.0259 Hz- 13.307 Hz following quenches from above to below the glass transition temperature (Tg). It is found that understanding and eliminating various artifacts such as signal drift, non-stationary responses, extraneous noise spikes due to differential thermal contractions, also reducing the effect of spectral leakage due to the finite Fourier transform artifacts and a carful background signal subtraction are very important for accurately determining effective temperature. We find moderate FDR violations, which remain clearly above the bath temperature for more than 100s after quench for frequencies < 0.4159 Hz. This corresponds to f tw>10, much larger than for spin glasses. However, we also detect a very strong violations which rapidly decay, with Teff >103, for the lowest frequencies and shortest aging times, tw. Our measurements of the dielectric response in glassy polymers at the equilibrium and aging regime in frequency range of 10-3 to 105 Hz provide a direct analogy with the magnetic-susceptibility aging studies in spin glasses. We can then examine if the theories proposed for spin glasses have relevance for glassy polymers. The results of these experimental studies are important in understanding the relaxation dynamics of glassy systems and in testing the validity and the relevance of the effective temperature concepts and also distinguishing between different theoretical models.

Document Type

Dissertation

Rights Information

Copyright 2008

Rights Holder

Hassan Oukris


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