Behavior of lattice parameter in cholesteric blue phases

Abstract
The blue phases (BP) in a system of chiral biphenyl mixtures have been studied in detail. It is found that when the cholesteric pitch is below a critical value, two BPII lattice parameters coexist, with the shorter one being dominant and the longer one transforming continuously from the BPI lattice. The relative contraction of the dominant lattice at the BPI-BPII transition is apparently universal. Above the critical pitch, the shorter BPII lattice vanishes.