Junmei Ji

Abstract

In this project, the effect of melt annealing on the crystallization of poly(ethylene oxide), (PEO), was studied by comparing thermal annealing to microwave annealing. After the subsequent controlled crystallization, the crystalline morphology of films was characterized by Polarizing Light Microscopy (PLM); the melting curves for both films and bulk samples were measured by Differential Scanning Calorimetry (DSC). These measurements revealed significant differences between microwave and thermally annealed samples. We propose that microwave annealing has a "quantum on polymer crystallization. The difference in morphology cannot be explained by a change in the temperature profile of the two annealing methods. By investigating the difference between microwave annealing and thermal annealing, while changing the crystallization temperature, we found that microwave absorption could change the polymer chain conformation more efficiently. The application of microwaves accelerates the dipole moment oscillation thus speeding up rotation of polymer chain segments. In this way, microwave annealing could destroy the residual nuclei left from a prior crystalline morphology, decreasing the nucleation site density. Consequently, homogeneous nucleation becomes more important in the case of microwave annealing, and the morphology and melting behavior of the crystalline phase are both changed. As molecular weight of PEO was increased, the microwave effect became more evident. Some factors in the crystallization process which may mask the microwave effects are the surface area of the film samples, the cooling rate and the crystallization temperature. It is believed that microwave annealing has potential to produce new crystalline polymeric materials with different solid state microenvironments, as compared to thermal annealing. It may give a method to control the crystallization process, and provide a new way to perform kinetic and thermodynamic studies on semicrystalline polymers.

Library of Congress Subject Headings

Polymers; Crystallization; Annealing of crystals

Publication Date

11-1-1998

Document Type

Thesis

Department, Program, or Center

School of Chemistry and Materials Science (COS)

Advisor

Langner, Andreas

Comments

Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works. Physical copy available through RIT's The Wallace Library at: QD937 .J5 1998

Campus

RIT – Main Campus

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