• Saubern, Simon
• Hornung, Christian
• Kyi, Stella
• Nguyen, Xuan

Abstract

In recent years, Reversible Addition Fragmentation Chain Transfer (RAFT) polymerisation has been extensively explored by academic and industry researchers due its ability to control the molecular weights, compositions and architectures of the resulting polymers. RAFT polymerisation is usually conducted in batch process where the solution containing chain transfer agent, monomer(s) and initiator is carefully deoxygenated by either freeze-pump-thaw or nitrogen bubbling prior to heating in a sealed vessel.Although it is a convenient and versatile process, the steps involved are laborious, time consuming and may require specialised glassware.In addition, scaling up is limited due to uneven heat transfer within the reaction vessel and oxygen sensitivity. Here we report a new processing method where RAFT polymerisation is performed under continuous flow conditions using a laboratory scale tubular flow reactor system.The flow reactor system is a modular unit consisting of a series of microtubular reactors that use fluidic pumping systems.Starting materials are injected through precision manufactured reactor coils with controlled mixing and temperature. This process enables multi-step synthesis such as polymerisation of block or multi-block copolymers to be obtained sequentially.A series of different acrylates, acrylamides and vinyl acetate based homopolymers and block copolymers were obtained via the flow process in high conversion (80%-100%) at temperature between 70˚C and 100˚C using various chain transfer agents, initiators and solvents with average molecular weights and dispersity (1.1-1.2) comparable to that of batch process.The applicability of RAFT polymerisation in continuous flow systems represents an effective method to access high quality polymers in large scale without the need for isolation of hazardous, reactive or odorous intermediates. By using multistep processing, the system can readily be modified to include an in-line degasser, multiple reactors, in-line analysis systems such as a UV detector as well as in-line purification.

Topics

• impedance spectroscopy
• Oxygen
• reactive
• Nitrogen
• molecular weight
• copolymer
• homopolymer
• block copolymer