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Effect of nonmesogenic crosslinking units on the mesogenic properties of side-chain cholesteric liquid crystalline elastomers

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Abstract

A series of cyclosiloxane-based cholesteric liquid crystalline elastomers were synthesized by using cholest-5-en-3-ol(3β)-4-(2-propenyloxy)benzoate and a soft nonmesogenic crosslinking agent, acryloyl-hexyl acrylate. The polymers were prepared in a one-step reaction with the crosslinking contents ranging between 0 and 5.6 weight %. The effective crosslink density (Mc) was determined by swelling experiments employing Flory–Rehner models. All the polymers exhibited thermotropic LC properties and revealed a cholesteric phase. With increase of the crosslinking component in the polymers, the melting behavior disappeared and the enthalpy of transition decreased. But the temperature of glass transition and clear point changed little and did not show uptrend or downtrend. Reflection spectra of the cholesteric mesophase of the polymers showed that the reflected wavelength became broad and shifted to long wavelength with increase of the soft crosslinking component in the polymer systems. All these results originate from the effect of the soft nonmesogenic chemical crosslinking. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 625–631, 2005

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