SPECIFIC OPTICAL-PROPERTIES OF BLENDS OF CHOLESTERIC COPOLYMERS

The phase behaviour of cholesterol containing liquid crystalline (LC) copolymers of different compositions (copolymers A and B), and the pha se behaviour and optical properties of their blends have been investig ated. The phase diagram of the mixture consisting of two fractions A a nd B with low molecular masses (M-W<10(4)) corresponds to complete sol ubility of the components over the whole concentration range. The tran smittance spectrum of all blends has one minimum, which lies between t wo peaks corresponding to the wave lengths of the initial samples A an d B. In the case of the cholesteric copolymers with molecular masses a bove 10(4), the corresponding phase diagram exhibits a lower critical solution temperature (T-crit). Below T-crit only one peak of the selec tive reflection of light is observed (SRL). However, above T-crit two separate bands of SRL, corresponding to the reflection bands for the i ndividual initial copolymers A and B are observed. The process of appe arance of the single or double bands is reversible and by varying the temperature one can obtain films with bimodal or unimodal curves of SR L.