4-cyano-4′-octylbiphenyl

Description

4-cyano-4′-octylbiphenyl is a calamitic (rod-shaped) mesogen based on a biphenyl core terminated by an octyl chain. Molecules of this shape share a common director, and that orientational order – fluid in position, ordered in direction – is what a liquid crystal device switches.

Key data

• Catalogue code: KC1014
• CAS number: 52709-84-9
• Molecular formula: C21H25N
• Molecular weight: 291.43 g/mol
• Category: Liquid Crystals
• Also listed as: 4′-Octyl[1,1′-biphenyl]-4-carbonitrile

What the substitution pattern does

The octyl chain places this compound at n=8 in its homologous series. Chain length is not a cosmetic variable here: each added methylene lowers the melting point unevenly and shifts the balance between nematic and smectic order, because a chain with an even number of carbons projects its terminal bond at a different angle to the molecular long axis than an odd one. Homologues therefore alternate in behaviour rather than trending smoothly, and an even-numbered member frequently outperforms both of its neighbours for a given formulation.

At this chain length the aliphatic volume starts to dominate. Long chains favour layered smectic packing over the nematic phase and increase solubility in non-polar media, which matters as much for work-up as for the final material.

The biphenyl core supplies the rigid, elongated shape that mesophase formation requires. Its two rings twist out of coplanarity by roughly 40 degrees in the gas phase but flatten in condensed phases, and that adjustable conjugation is what makes biphenyls both mesogenic and optically anisotropic.

Phase behaviour

Transition sequence measured for this compound:

Crys 21.5 SmA 33.5 N 40.5°C I

Reading that sequence, in order of increasing temperature:

• Crys – crystalline solid
• SmA – smectic A – layered, molecules normal to the layers
• N – nematic – orientational order without layers
• I – isotropic liquid

The mesophase window spans roughly 19.0 K above the melting point. Width of that window, not its position alone, decides whether a compound is usable neat or only as one component of a eutectic mixture.

Typical applications

• smectic-phase studies where a long terminal chain is required
• extension of rigid-core length in high-birefringence blends
• positive-dielectric-anisotropy hosts driven by the terminal nitrile
• nematic and smectic host mixtures for display and photonic devices
• reference material for calibrating transition temperatures and optical measurements

Ordering

This compound is supplied to order. Pricing depends on quantity and on the specification you need, so it is quoted rather than listed – send an enquiry stating the quantity and any purity or analytical requirement, and you will receive a written quotation.

Please quote CAS 52709-84-9 or catalogue code KC1014 when enquiring, so that the correct isomer is supplied.

Handling and documentation

Supplied for laboratory and industrial use by trained personnel only. Not for use as a medicine, food, cosmetic or biocide, and not for administration to humans or animals. Safety documentation is issued with the order; this page is not a source of hazard information.