AbstractWe present a simplified model for calculating the product distribution of degradable polymers which is based on a grand canonical approach. The distribution depends on two physical parameters, the energy of a bond formation and the initial concentration of monomers. Due to its simplicity this model covers the two limiting cases, namely a polymerization process (no degradation) and micellar association (dominant degradation), and allows for straightforward extension to branched chain topologies or flow fields. In shear flow, a flow rate dependent length distribution leads to shear thinning.