A single reactor process for formation of block copolymers comprising aromatic ester mesogenic units containing flexible alkane spacers and polyester flexible coil units in the main chain thereof which comprises reacting an .alpha.,.omega.-bis(hydroxybenzoyloxy) alkane monomer with an aromatic acid chloride in the presence of a functionalized flexible coil oligomer under temperature conditions in which an acid chloride-terminated bis(hydroxyalkyl terephthalate) oligomer was first formed at a first, lower temperature and the block copolymer was then formed at a second, higher temperature by reacting this oligomer with the functionalized flexible coil oligomer.