An infrared study of Langmuir–Blodgett films of side-chain chiral liquid crystalline polysiloxane

Abstract

Langmuir films of a side-chain ferroelectric liquid crystalline polysiloxane of 4-(10-undecen-1-oyloxy)-4′-(s)-2-methybutoxybiphonyl (P(III)) and its monomer 4-(10-undecen-1-oyloxy)-4′-(s)-2-methybutoxybiphonyl (M(III)) were transferred successfully at surface pressures of 11 and 8 mN m−1 onto solid substrates, respectively. The π–A isotherms of P(III) and M(III) have shown that they have different properties on the air/water interface. The monolayer film on the air/water interface of M(III) shows a clear orientation transition while that of P(III) does not. Infrared (IR) transmission and reflection–absorption spectra of Langmuir–Blodgett (LB) films of P(III) and M(III) indicate that the long axis of the chromophoric part of P(III) is almost perpendicular to the substrate surface while that of M(III) is tilted with respect to the substrate normal. The alkyl parts of both P(III) and M(III) are tilted considerably from the substrate normal. It also indicated from the IR spectra of the LB films that the liquid crystalline molecules of P(III) and M(III) are highly ordered and oriented in the monolayer and multilayer LB films. Temperature-dependent IR experiments show that the alkyl chains have anisotropic property in both P(III) and M(III). This may be due to the influence from the chiral groups of the molecules rather than from the substrates, and the side chains of P(III) play an important role in enhancing the anisotropic property.