Volume Phase Transitions of Heliconical Cholesteric Gels under an External Field along the Helix Axis

We present a mean field theory to describe cholesteric elastomers and gels under an external field, such as an electric or a magnetic field, along the helix axis of a cholesteric phase. We study the deformations and volume phase transitions of cholesteric gels as a function of the external field and temperature. Our theory predicts the phase transitions between isotropic (I), nematic (N), and heliconical cholesteric ([Formula: see text] phases and the deformations of the elastomers at these phase transition temperatures. We also find volume phase transitions at the [Formula: see text] and the [Formula: see text] phase transitions.