The optically isotropic phases (high-temperature I₁ and low-temperature I₂) separated by the first order phase transition with melting temperature 1.5-2.3 kJ/mol found in previously synthesized comb-shaped copolymers CB-AA6-x with mesogenic alkoxycianobiphenyl (CB) side groups and isophthalic acid (AA6) side groups were investigated. Through studying Kerr effect in isotropic melt the new I₂ phase was identified as really isotropic. It is established that at phase transition I₁↔I₂ the local orientation order value does not undergo jump changing and temperature dependence of orientation order in the I₂ phase is absent. This means that in I₂ phase changing of close orientation order is probably sterically hindered that is due to microphase segregation of mesogenic and acid groups.