The fundamental thermal and optical properties of a side-chain cholesteric liquid crystal silicone, which forms a single blue phase, were investigated. In particular. we examined the optical activity of the isotropic and blue phase for fields varying from zero to approximately 10(6) Vm(-1). The zero-field optical activity data is not consistent with theoretical predictions. Optical microscopy, Bragg reflections and thermal analysis were also used to further characterize the properties of the liquid crystalline phases.