The synthesis and detailed structural characterization of phthalocyanine derivatives substituted by six dodecyloxy side chains and a single poly(oxyethylene) moiety are described. All of the materials possess columnar mesogenic properties. The phthalocyanines attached to short poly(oxyethylene)s possess an ordered hexagonal mesophase (D-ho) of structure similar to that obtained from octakis(dodecyloxy)phthalocyanine. However, the Pc attached to a long poly(oxyethylene) side chain displays a less ordered columnar mesophase, probably columnar nematic (N-c), due to steric disturbance of the two-dimensional hexagonal lattice by the polymeric substituent. This material also displays an interesting phase separation of the poly(oxyethylene) and alkoxy side chains in the solid state.