Linear viscoelasticity of side chain liquid crystal polymer

Ralph H. Colby, J. R. Gillmor, G. Galli, M. Laus, C. K. Ober, E. Hall

Research output: Contribution to journalArticlepeer-review

59 Scopus citations

Abstract

Small amplitude oscillatory shear has been used to study thermotropic liquid-crystalline polymers that have mesogenic groups pendant to flexible backbones. The polymers studied form nematic and smectic glasses, enabling viscoelastic response to be studied over a wide range of frequencies using time-temperature superposition. In contrast to main chain liquid-crystalline polymers, the nematic side chain polymers exhibit linear viscoelastic response over a wide range of strain amplitudes that is independent of thermal and shear histories. Viscoelastic response is very sensitive to smectic-nematic and smectic-isotropic transitions, but insensitive to the nematic-isotropic transition, as time-temperature superposition applies across this transition. We compare viscoelastic data with diffusion data by calculating the time τ that it takes a polymer to diffuse a distance equal to its coil size R (τ=R2/D). At frequencies lower than 1/τ side chain polymers in their nematic show the terminal response characteristic of viscoelastic liquids. In their smectic, they are still strongly viscoelastic at frequencies lower than 1/τ and approach the terminal response of a viscoelastic solid at the lowest frequencies. Implications of such behaviour are discussed.

Original languageEnglish (US)
Pages (from-to)233-245
Number of pages13
JournalLiquid Crystals
Volume13
Issue number2
DOIs
StatePublished - Jan 1 1993

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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