CAS NO.95973-51-6 4-Ethoxyphenyl 4-trans-(4-pentylcyclohexyl)benzoate

Frequently Asked Questions

Q1: What is CAS NO.95973-51-6?

CAS NO.95973-51-6 is 4-ethoxyphenyl 4-trans-(4-pentylcyclohexyl)benzoate, a three-ring nematic liquid crystal compound with molecular formula C26H34O3 and molecular weight 394.55 g/mol. The molecule consists of a trans-4-n-pentylcyclohexyl group linked to a benzoic acid ring, which is esterified with 4-ethoxyphenol. It is a member of the phenylcyclohexyl (PCH) ester mesogen family, widely used in formulating nematic liquid crystal mixtures for display and photonic applications. The MDL number is MFCD09952999 and the PubChem CID is 23334669.

Q2: What is the significance of the trans configuration on the cyclohexane ring?

The trans configuration of the 1,4-disubstituted cyclohexane ring is essential for liquid crystallinity. In the trans isomer, both the pentyl chain and the benzoate group occupy equatorial positions, producing a highly linear, rod-like molecular shape that packs efficiently into a nematic phase. The cis isomer has one axial substituent, creating a bent conformation that disrupts long-range orientational order and typically eliminates the mesophase entirely. Commercial-grade material is therefore specified as the trans isomer with high stereochemical purity.

Q3: What are the key physical properties?

The compound has a predicted boiling point of approximately 522 °C at 760 mmHg, a predicted density of about 1.034 g/cm³, and a flash point around 227 °C. It appears as a white solid at room temperature. The logP is approximately 7.16. Storage at 2–8 °C under inert atmosphere is recommended for long-term stability. The trans-cyclohexylbenzoate core provides good chemical and photochemical stability compared to all-aromatic analogues.

Q4: How does the ester linkage influence liquid crystal behavior?

The benzoate ester group connecting the two aromatic rings serves multiple functions. It increases the molecular length-to-width ratio, raising the clearing temperature and broadening the nematic phase range. The carbonyl group introduces a longitudinal dipole moment that contributes to dielectric anisotropy. Additionally, the ester linkage provides a degree of molecular flexibility that helps lower the melting point compared to a directly linked biphenyl analogue, making the compound more practical for mixture formulation at room temperature.

Q5: What is the role of the ethoxy terminal group?

The 4-ethoxy group on the terminal phenol ring is a short alkoxy substituent that donates electron density into the aromatic system through resonance. This increases the longitudinal dipole moment and contributes to the compound’s dielectric anisotropy. Compared to a methoxy group, the ethoxy group slightly increases molecular width and lowers the melting point, improving room-temperature mixture compatibility. Compared to longer alkoxy chains (propoxy, butoxy), it provides a higher clearing point relative to viscosity, making it a good compromise for high-performance mixtures.

Application Cases

Application Case 1: TN-LCD Mixture for Industrial Instrumentation

A display manufacturer required a nematic mixture with a wide operating temperature range (−30 to 85 °C) for industrial process control panels. 4-Ethoxyphenyl trans-4-(4-pentylcyclohexyl)benzoate was incorporated at 12–18 wt% alongside cyanobiphenyl and bicyclohexyl co-components. The ester mesogen raised the mixture clearing point above 100 °C while maintaining acceptable viscosity, and the trans-cyclohexyl group ensured reliable performance under thermal cycling. The final formulation met the contrast ratio and response time specifications for the industrial TFT module.

Application Case 2: VA-Mode Television Panel Formulation

An LCD panel developer used this compound as part of a negative dielectric anisotropy mixture for MVA/PVA television panels. The linear three-ring structure promoted stable homeotropic alignment on the rubbed polyimide layer, and the high resistivity of the purified material (ρ > 10¹³ Ω·cm) supported the low-power active-matrix driving scheme. Blended with difluoro-substituted co-mesogens to tune Δε to approximately −3.5, the compound contributed to a high contrast ratio of over 4000:1 in the prototype panel.

Application Case 3: Automotive Dashboard Display Under Extreme Temperatures

A Tier 1 automotive supplier needed an LC mixture that maintained fast response at −40 °C and resisted degradation at 105 °C for vehicle dashboard displays. This mesogen was selected for its high flash point and thermal stability. The trans-cyclohexylbenzoate core withstood prolonged high-temperature operation without phase separation or isomerization, while the pentyl terminal chain helped keep the low-temperature viscosity manageable. The mixture passed 1000-hour thermal aging tests with no measurable shift in threshold voltage.

Application Case 4: Nematic Mixture for Optical Phase Modulator

A photonic research group developing a liquid-crystal spatial light modulator required a nematic mixture with high birefringence (Δn > 0.15) and low rotational viscosity for fast phase switching at 1550 nm. This compound was blended with high-birefringence terphenyl co-mesogens to raise Δn while using the cyclohexyl moiety to suppress viscosity. The ester-type mesogen improved mixture compatibility and prevented crystallization during the device’s operating cycle, enabling 2π phase modulation at under 5 V with sub-millisecond response at elevated driving temperatures.

Application Case 5: Structure-Property Reference Standard in LC Research

A university liquid crystal laboratory used high-purity 4-ethoxyphenyl trans-4-(4-pentylcyclohexyl)benzoate as a reference compound for an X-ray diffraction and DSC study of alkoxy-terminated PCH esters. The single-isomer trans material provided reproducible smectic-nematic and nematic-isotropic transition temperatures, allowing the researchers to correlate terminal chain length with orientational order parameter and layer spacing. The data served as a calibration point for their molecular dynamics simulation model of ester-type mesogens.