Dielectric relaxation spectroscopy of amorphous and liquid-crystalline side-chain polycarbonates

✍ Scribed by Michael Wübbenhorst; Ernout M. Van Koten; John C. Jansen; Wim Mijs; Jan van Turnhout

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 437 KB
• Volume: 18
• Category: Article
• ISSN: 1022-1336
• DOI: 10.1002/marc.1997.030180211

✦ Synopsis

Abstract

The molecular dynamics of amorphous and liquid‐crystalline (LC) side‐chain polycarbonates was studied by dielectric spectroscopy at frequencies from 10^−2^ to 10^6^ Hz and at temperatures from −160 to 180°C. ‘Model’ compounds containing no mesogenic side‐groups showed two relaxations, which originate from the carbonate group (α, β~m~‐relaxation). By contrast, in LC‐polycarbonates bearing a mesogenic nitrostilbene side group around and above the glass transition temperature T~g~ up to three relaxation modes were distinguished (α‐, λ~1~‐, λ~2~‐process); below T~g~ four secondary relaxations (γ‐, β~m~‐, β~s~‐, β~sc~‐relaxation) were observed. The γ‐relaxation was found only in compounds possessing an aliphatic spacer linked to the backbone by an ether bond. Apart from β~m~‐, two additional β‐processes were identified as relaxations associated with the mesogenic unit in the glassy (β~s~) or in the crystalline state (β~sc~).