Doctoral Dissertations

Date of Award

5-1970

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Chemistry

Major Professor

Dr. Ffrancon Williams

Committee Members

Ralph Livingston, W.W. Parkinson Jr., Lida K. Barrett, William Fletcher

Abstract

Trapped electrons have been detected by ESR spectroscopy in poly ethylene, isotactlc polypropylene, and poly(U-methylpentene-l) following 7-irradiation at 77°K. In all cases, the ESR spectrum consists of a narrow singlet at g = 2.0023 ± 0.0002 superimposed on a broad free radical spectrum. The singlet can he photobleached by near infrared light (A > 1000 nm) and is readily saturated at low microwave powers. The singlet is assigned to a trapped electron since this behavior is analogous to that known to be characteristic of trapped electrons in 7-irradiated alkane glasses.

Initial G-values for trapped electrons in these systems range from O.kG for linear polyethylene down to O.O8 for isotactic poly(i+-methylpentene- l). Both G-values and the maximum value attained in the concentration-dose curve for trapped electrons appear to he correlated with the crystallinity of the polymer and decrease with decreasing crystallinity. Little or no trapped electrons could be detected in non-crystalline polymers such as atactic polypropylene or polyisobutylene. These results strongly suggest that the electron trap is associated with crystalline regions of the polymer.

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