(268f) Polymer Microsphere Synthesis by Membrane Emulsification

A major driver for innovation in the application of polymer products can be found in the ability to produce well-defined monodisperse polymer particles, allowing the controlled release or dissolution patterns in drug formulations or specific particle sizes for printer toners. Especially in the range between 1 and 10 μm no current technology is able to produce this type of particles. Additionally, particles consisting of polymer blends or containing functional (solid) additives are often required. This is virtually impossible with existing techniques. It is expected that emulsification using micro-engineered membranes allows for the production of polymer particles with a narrow particle size distribution by choosing the appropriate membrane specifications, temperature and surfactant type and concentration.^[1,2]

In this work, available emulsification systems are adapted for use with complex dispersed phases. The final aim is to produce dispersed solid particles. This is done by emulsification of monomer droplets, followed by polymerization or by droplet formation of concentrated polymer solutions or melts. Emulsification experiments are conducted in a cross-flow membrane setup, see Figure 1.

Figure 1. Schematic illustration of the membrane emulsification setup

The droplets formed are polymerized during or after the droplet formation process. Polymerization should be very fast, to avoid coalescence and to avoid the use of substantial amounts of surfactants. However, it should not be so fast that the microchannels become fouled or plugged during emulsification. The time constants of emulsification and polymerization should be closely linked. It is expected that initiating the polymerization during or perhaps even before emulsification can lead to a dramatic change in the emulsification process. Thus, the interplay between loaded dispersed phase, polymerization and emulsification processes are central here.

References

   [1]    A.J.Abrahamse, R.van Lierop, R.G.M.van der Sman, A.van der Padt, and R.M.Boom, "Analysis of droplet formation and interactions during cross-flow membrane emulsification," Journal of membrane science, vol. 204 pp. 125-137, 2002.

   [2]    S. van der Graaf, C. G. P. H. Schroen, R. G. M. van der Sman, and R. M. Boom, "Influence of dynamic interfacial tension on droplet formation during membrane emulsification," Journal of Colloid and Interface Science, vol. 277, no. 2, pp. 456-463, 2004.