Non-symmetric liquid crystal trimers

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Abstract

Four homologous series of non-symmetric linear liquid crystalline trimers, the 4-[(4-{n-[4-(4-methoxy-phenylazo)phenoxy]alkyloxy}benzylidene)amino]benzoic acid 6-[4-(4-methoxyphenylazo)phenoxy]hexyl esters, 4-[(4-{n-[4-(4-cyanophenylazo)phenoxy]alkyloxy}benzylidene)amino]benzoic acid 6-[4-(4-methoxyphenylazo)phenoxy]hexyl esters, 4-[(4-{n-[4-(4-methoxyphenylazo)phenoxy]alkyloxy}benzylidene)amino]benzoic acid 6-[4-(4-cyanophenylazo)phenoxy]hexyl esters and 4-[(4-{n-[4-(4- cyanophenylazo)phenoxy]butoxy}benzylidene)amino]benzoic acid 6-[4-(4-cyanophenylazo)phenoxy]hexyl esters, have been synthesized and characterized. In each series one spacer was held constant while the length of the second was varied from 3 to 12 methylene units. All these trimers were nematogenic and exhibited pronounced odd-even effects in both their clearing temperatures and associated entropies. Only two of the trimers exhibited a smectic phase, and specifically those containing two differing terminal mesogenic groups and an undecyl spacer. This strongly suggests the driving force for smectic phase formation is a combination of molecular shape and a specific interaction between unlike mesogenic units. The smectic phase has been assigned as a triply-intercalated alternating smectic C phase, the first example of its kind.

Original languageEnglish
Pages (from-to)673-682
Number of pages9
JournalLiquid Crystals
Volume32
Issue number6
DOIs
Publication statusPublished - Jun 2005

Keywords

  • smectic-C-phase
  • mesophase properties
  • oligomers
  • polymers
  • lengths
  • dimers

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