Molecular dynamics of a main-chain liquid crystalline polyester below the crystalline to nematic phase transition

Valeria Arrighi, Julia S. Higgins

Research output: Contribution to journalArticle

Abstract

We present a quasielastic neutron scattering (QENS) study of a main-chain liquid crystalline polyester (LCP) containing 4,4'-dihydroxy-a,a'-dimethylbenzalazine as the mesogenic unit. The elastic neutron scattering intensity was monitored in the temperature range 2-400 K, below the crystalline to nematic phase transition (Tm = 423 K). Two selectively deuteriated LCPs were investigated: (a) a polymer deuteriated in the mesogenic units (mD-LCP) and (b) a polymer deuteriated in the flexible spacers (flD-LCP). This made it possible to distinguish the dynamics of the rigid mesogens from the molecular motion of the flexible spacers. A single process was detected in mD-LCP which reflects the motion of the alkyl chains whereas flD-LCP shows an additional low-temperature process which was attributed to reorientational motion of the methyl groups in the mesogens. The slow processes in mD-LCP and flD-LCP are similar, suggesting strong coupling between the dynamics of the flexible chains and the mesogens.

Original languageEnglish
Pages (from-to)1605-1612
Number of pages8
JournalJournal of the Chemical Society, Faraday Transactions
Volume93
Issue number8
Publication statusPublished - 21 Apr 1997

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polyesters
molecular dynamics
liquids
spacers
neutron scattering
polymers
elastic scattering

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abstract = "We present a quasielastic neutron scattering (QENS) study of a main-chain liquid crystalline polyester (LCP) containing 4,4'-dihydroxy-a,a'-dimethylbenzalazine as the mesogenic unit. The elastic neutron scattering intensity was monitored in the temperature range 2-400 K, below the crystalline to nematic phase transition (Tm = 423 K). Two selectively deuteriated LCPs were investigated: (a) a polymer deuteriated in the mesogenic units (mD-LCP) and (b) a polymer deuteriated in the flexible spacers (flD-LCP). This made it possible to distinguish the dynamics of the rigid mesogens from the molecular motion of the flexible spacers. A single process was detected in mD-LCP which reflects the motion of the alkyl chains whereas flD-LCP shows an additional low-temperature process which was attributed to reorientational motion of the methyl groups in the mesogens. The slow processes in mD-LCP and flD-LCP are similar, suggesting strong coupling between the dynamics of the flexible chains and the mesogens.",
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Molecular dynamics of a main-chain liquid crystalline polyester below the crystalline to nematic phase transition. / Arrighi, Valeria; Higgins, Julia S.

In: Journal of the Chemical Society, Faraday Transactions, Vol. 93, No. 8, 21.04.1997, p. 1605-1612.

Research output: Contribution to journalArticle

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