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Controlling Crystal Microstructure To Minimize Loss in Polymer Dielectrics

Miranda, Daniel F.; Zhang, Shihai; Runt, James

By 12 March 2019 April 22nd, 2019 No Comments

Macromolecules, 2017, vol 50, 20, pp. 8083-8096

DOI:10.1021/acs.macromol.7b01450

Abstract

A model semicrystalline polymer, poly(ethylene naphthalate) (PEN), was used to examine how morphological factors inhibit chain segment relaxations that contribute to dielectric loss. This was achieved by manipulating the extent of crystallization and the crystalline microstructure through a combination of annealing and uniaxial drawing and investigating the effects on dielectric performance. Varying crystallization conditions influenced the dynamic Tg and extent of rigid amorphous fraction formation but had only a moderate effect on loss magnitude. Film orientation, however, greatly reduced loss through strain-induced crystallization and the development of oriented amorphous mesophasic regions. Postdrawing annealing conditions were capable of further refining the crystal microstructure and, in turn, the dielectric properties. These findings demonstrate that the semicrystalline polymer morphology can have a very significant influence on amorphous chain relaxations that contribute to dielectric loss, and understanding how processing conditions affect morphology is critical to the rational design of polymer dielectrics.

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