This paper describes the synthesis and characterization of the polyethers based on 1-(4-hydroxyphenyl)-2-(2-methyl-4-hydroxyphenyl) ethane (MBPE) and 1,15-dibromopentadecane (MBPE-15), MBPE and 1,16-dibromohexadecane, and of the copolyethers based on MBPE and 1,8-dibromooctane with 1,15-dibromopentadecane (MBPE-8/15), and with 1,16-dibromohexadecane (MBPE-8/16). MBPE-15 and MBPE-16 are only crystalline while MBPE-8/15 and MBPE-8/16 display a monotropic or even an enantiotropic nematic mesophase. The virtual isotropic-nematic transition temperature of MBPE-15 determined from these copolymers is 62°C (ΔH=2.58 kcal/mru), while the virtual isotropic-nematic transition temperature of MBPE-16 is 73°C (ΔH=3.15 kcal/m