Aliphatic polycarbonates are a relatively new class of polymer, which are characterized by an instability at the functional group, which makes them easily degraded and capable of biodegradation; as such, they constitute a potentially powerful group of polymers for exploitation in green technology. Rheological properties in shear flow are presented for the seven following different aliphatic polycarbonate samples: polyethylene carbonate, polypropylene carbonate, linear pentene polycarbonate, linear hexene polycarbonate, linear octene polycarbonate, cyclohexene polycarbonate, copolymer of propylene oxide (20%), and cyclohexene oxide (80%), using parallel plate rheometry. No studies of the rheological properties of aliphatic polycarbonates have been reported in the literature to date. The steady-state and the dynamic properties of these new polymers are investigated, and the resulting flow curves and the dynamic relaxation spectra of the aliphatic polycarbonate melts are presented. One of the major problems encountered in trying to characterize the melt rheology and relate behavior to the underlying molecular structure is the instability of the polymers. Because of this, a narrow processing window is present for each polymer, and it makes it impossible to compare all polymers at a constant temperature or range of temperatures in the melt. Nevertheless, some progress can be made. In all cases, the rheological response is discussed in terms of molecular characteristics, in particular, the length of the side chain and the molecular weight distribution. (C) 2004 Wiley Periodicals, Inc.