Dielectric behavior of some aromatic polyimide films

Stefan Chisca*, Valentina Elena Musteata, Ion Sava, Maria Bruma

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

109 Scopus citations

Abstract

Aromatic polyimides were prepared by polycondensation reaction of two aromatic diamines, such as 4,4′-diaminodiphenylmethane (DDM) and 3,3′-dimethyl-4,4′-diaminodiphenylmethane (MDDM), with aromatic dianhydrides, such as 4,4′-isopropylidene-diphenoxy-bis(phthalic anhydride) (6HDA), benzophenonetetracarboxylic dianhydride (BTDA) and hexafluoroisopropylidene-bis (phthalic anhydride) (6FDA). These polymers are soluble in polar aprotic solvents and can be cast into thin films from such solutions. The polyimides show high thermal stability, with decomposition temperature being above 430 °C in air, and high glass transition temperature being in the range of 200-287 °C. The free standing films, having the thickness of tens of micrometers, exhibited good mechanical and electrical insulating properties. The dielectric constant, molecular mobility and AC conductivity of thin films prepared from these polymers were investigated in detailed. The study of their dielectric behavior evidenced low dielectric constant values, in the range of 2.88-3.48 at 1 Hz at room temperature, and three relaxation processes (γ, β1 and β2) were observed at sub-glass temperatures for polyimides based on 6HDA and 6FDA and only two (γ and β) relaxations were detected for polyimides based on BTDA. The cooperativity of the molecular motions associated with the relaxation processes was discussed.

Original languageEnglish (US)
Pages (from-to)1186-1197
Number of pages12
JournalEuropean Polymer Journal
Volume47
Issue number5
DOIs
StatePublished - May 2011
Externally publishedYes

Keywords

  • AC conductivity
  • Dielectric properties
  • Dielectric relaxation
  • Polyimide

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Polymers and Plastics
  • Organic Chemistry

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