Phase chirality and stereo-selective swelling of cholesteric elastomers.
Cholesteric elastomers possess a macroscopic "phase chirality" as the director n rotates in a helical fashion along an optical axis z and can be described by a chiral order parameter alpha. This parameter can be tuned by changing the helix pitch p and the elastic properties of the network at formation. The cholesterics also possess a local nematic order, changing with temperature or during solvent swelling. In this paper, by measuring the power of optical rotation d upsilon /dz , we discover how these two parameters vary as functions of temperature or solvent adsorbed by the network. The main result is a finding of pronounced stereo-selectivity of cholesteric elastomers, demonstrating itself in the retention of the "correct" chirality component of a racemic solvent. It has been possible to quantify the amount of such stereo-separation, and the basic dynamics of the effect.
Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge, CB3 0HE, UK.
S
S
Courty
A R
AR
Tajbakhsh
E M
EM
Terentjev
D002152:Calorimetry, Differential Scanning; D002784:Cholesterol / Q000737:chemistry*; D002942:Circular Dichroism; D020724:Elastomers / Q000737:chemistry*; D046911:Macromolecular Substances; D008422:Materials Testing; D008958:Models, Molecular; D008968:Molecular Conformation; D044367:Phase Transition; D012997:Solvents / Q000737:chemistry*; D013237:Stereoisomerism; D013696:Temperature
D020724:Elastomers; D046911:Macromolecular Substances; D012997:Solvents; D002784:Cholesterol