Description:
Macroporous polymers with tailored properties can be synthesised by polymerisation of water-in-monomer high internal phase emulsions (HIPEs). HIPEs are highly viscous, paste like emulsions in which an internal phase, usually defined as constituting more than 74% of the emulsion volume, is dispersed within a continuous external minority phase. Macroporous polymerised HIPE beads can be produced using the same principles.
Of the various production methods, industry prefers suspension polymerisation as it is low cost and easily scalable. The main drawbacks are a wide range of particle size dispersity and low efficiency; this leads to a high level of waste as incorrectly sized particles must be removed.
Another method to produce porous polymer beads is the polymerisation of multiple emulsions, either by sedimentation polymerisation or in microfluidic systems. Both methods solve the problem of polydispersity but only work in a specific range of bead size, dependent on the setup and rheological properties of the emulsion used. In sedimentation polymerisation, droplets of emulsion are released and polymerised in an immiscible sedimentation medium. In microfluidics emulsion droplets dispersed in an immiscible carrier phase are exposed to UV light to achieve polymerisation. Polymerisation in microfluidic devices does achieve low polydispersity (variation coefficient or CV around 1-5%) but at the disadvantage of low production rates. Additionally, sedimentation is not a continuous process and the tubes used in microfluidics clog regularly.
This technology, polymerisation of emulsion droplets suspended in an immiscible carrier phase in a plug flow reactor, provides a continuous process for manufacturing macroporous beads based on microfluidics. The simple production method allows synthesis of large amounts of macroporous beads in different size ranges with a variation coefficient (CV) of 15-28%. This is higher than that of microfluidics but much lower than in suspension polymerisation.
• Simple to construct
• Large volume production without clogging
• Potential to scale up
• Highly adjustable
o bead size from 350μm to 1500 μm
o bead surface (open/close)
o bead inner pore structure (open/close)
• Mechanical performance defined by monomers used
• Encapsulation of active ingredients possible