The side reactions in the synthesis of oxyethylmethacrylate-functionalised poly(L-lactide) macromonomers using aluminium mono- and trialkoxides carrying this functionality have been studied. In addition to the expected changes in the final molecular weight for this kind of polymerisations, changes in the structure of the chain end-groups have been identified by spectroscopic techniques. Radical polymerisation of the functionalised macromonomers has also been detected, especially when dealing with low molecular weight prepolymers.