Broadband Dielectric Spectroscopy On the Molecular Dynamics in Different Generations of Hyperbranched Polyester Gamal Turky, 1 Shereen S. Shaaban, 1 Andreas Scho ¨ enhals 2 1 Microwave Physics and Dielectrics, National Research Center, Dokki, Cairo, Egypt 2 Federal Institute of Materials Research and Testing FG:VI.3, D-12205, Berlin, Germany Received 10 June 2008; accepted 11 January 2009 DOI 10.1002/app.30046 Published online 28 April 2009 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: Dielectric spectroscopy (10 2 Hz to 10 6 Hz) was employed to investigate the molecular dynamics of hyperbranched polyesters where the number of the gener- ation is systematically varied from 2 to 5. As a first result, the dielectric properties depends strongly on the genera- tion of the hyperbranched polymers. For higher genera- tions (3 to 5) at temperatures below T g two relaxation processes are observed, a c-process at lower temperatures and a b-process at higher ones. The apparent activation energies are around 100 kJ/mol which seems to be too high for truly localized processes. For the Generation 2, only the c-process is observed. For all investigated poly- mers the dielectric a-relaxation could not be observed because of strong conductivity effects. Therefore, the con- ductivity is systematically analyzed which obeys the pecu- liarities found to be characteristic for semiconducting disordered materials. Especially, the Barton/Nakajima/ Namikawa relationship is found to be valid. V V C 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 2477–2484, 2009 Key words: molecular dynamics; polyesters; relaxation; synthesis INTRODUCTION Dendrimers are highly branched, globular macromo- lecules with a great number of arms emanating from central core. 1,2 The stepwise synthesis of dendrimers affords molecules with highly regular branching pat- tern, a definite molecular weight, a low polydisper- sity index and a well-defined number of peripheral groups. 3 In recent years, dendritics (dendrimers, hyper branched and star polymers) have shown promise for different applications for instance in fields rang- ing from gene delivery to magnetic resonance imag- ing to the development of vaccines, antiviral, antibacterial and anticancer therapeutics. 4–7 A comparison of the features of dendritics with those of linear polymers shows that the dendritic architecture can provide several advantages for instance for drug delivery application. For example, the multivalency of dendritics can be used to attach several drug molecules, targeting groups and solubi- lizing groups to the periphery of the dendritics in a well defined manner. Furthermore, the more globu- lar shape of dendritics, as opposed to the random coil structure of most linear polymers, could affect their biological properties, leading to the discovery of interesting effects related to macromolecular architecture. Hyperbranched (hb) polymers on the other hand, can be synthesized by a one step method without many and tedious purifying techniques. This makes them advantageous over dendrimers in that sense. They retain the main features of dendritic macromo- lecules and show properties intermediate to those of dendritics and linear polymers. 8,9 These dominate the high potential for applications in, for example, coating and resin applications and as additives for linear polymers. Moreover, their use in high-tech applications, such as catalysis, microelectronics, thin- film technology, and sensorics as well as many other applications are increasing strongly. 10–29 The field of aliphatic hb polyesters with hydroxyl groups at the peripheral surfaces is dominated by products based on bishydroxy- methyl propionic or dimethylol propionic acid (DMPA). With the com- mercially available Boltorn* brands (from Perstorp) prepared by AB 2 þ B 3 approach with stepwise slow monomer addition as shown in Figure 1. They are polydisperse polymers i.e. no protection groups are used to control dendritic growth. Hyperbranched growth is instead controlled by stoichiometric ratios Journal of Applied Polymer Science, Vol. 113, 2477–2484 (2009) V V C 2009 Wiley Periodicals, Inc. Correspondence to: G. Turky (gamalturky@yahoo.com). *Boltron is a trademark of Perstop.