Polymerisation of Alkenes user 12 years ago Polymerisation of Alkenes The polymerisation is a process of combining monomer molecules together in a chemical reaction to form polymer chains.The molecule of alkenes can combine together through addition reaction to form a long chain polymer.In the reaction, alkene molecules undergo addition reaction at the temperature of 200°C and pressure of 1200 atm.Thousands of alkene molecule join together to form a long chain molecule called poly(ethene) – commonly called polythene.