A series of hyperbranched polyethylene imine (PEI) polymers functionalized with long aliphatic chains has been prepared and characterized. Their self-organization as a function of temperature has been investigated using differential scanning calorimetry, thermogravimetry and X-ray diffraction. Both lamellar (SmA, SmB) and columnar (rectangular) mesophases have been identified. From the detailed study of the parameters of these mesophases it turns up that hydrogen bonding between amide groups and the ordering of the long alkyl chains are the critical factors that determine the organization of the molecules and the formation of the mesophases. (C) 2012 Elsevier Ltd. All rights reserved.