Process to prepare alkylaminoxane by reacting, in the absence of solvent, 1 molar equivalent of alkylaluminium with 0.1 to 0.8 molar equivalent of a substituted allylic alcohol of the formula (I) wherein R1 and R2 are independently selected from aliphatic and aromatic hydrocarbon groups, and each R3, R4, and R5 is independently selected from aliphatic and aromatic hydrocarbon groups and a hydrogen atom.