Method of producing uniform polymer beads of various sizes
Speriodal polymer beads having a uniform size are prepared by polymerizing uniformly sized monomer droplets formed by dispersing a polymerizable monomer phase over a cross-flow membrane into an aqueous phase. A shear force is provided at a point of egression of the polymerizable monomer phase into the aqueous phase, the direction of shear substantially perpendicular to the direction of egression of the monomer phase. The polymer beads can be employed in applications where beads having uniform diameters of 10 to 180 μm are useful.
1. A method for preparing spheroidal polymer beads having a volume average particle diameter of about 10 to about 180 μm, the method comprising the steps of:
providing an apparatus comprising a metallic membrane containing a plurality of through holes, said through holes being conical or in the shape of a slot, wherein a first volume is in contact with a first side of the membrane and a second volume is in contact with a second side of the membrane, the first volume comprising a polymerizable monomer phase, the second volume comprising an aqueous liquid immiscible with the polymerizable monomer phase;
dispersing the first volume through the through holes into the second volume under conditions sufficient to form a plurality of monomer droplets comprising the polymerizable monomer, wherein a shear force is provided at a point of egression of the first volume into the second volume, the direction of shear substantially perpendicular to the direction of egression of the first volume, and the shear force is provided by displacing the membrane relative to the second volume; and
polymerizing the droplets dispersed in the second volume.
2. The method according to claim 1 , wherein the polymer beads exhibit a volume average particle diameter of about 35 to about 150 μm.
3. The method according to claim 1 , wherein the beads have a particle size distribution having a uniformity coefficient of less than 1.3.
4. The method according to claim 1 , wherein the displacing is rotating, pulsing, or oscillating movement.
5. The method according to claim 1 , wherein the first volume is dispersed into the second volume by applying pressure to the first volume.
6. The method according to claim 1 , wherein the monomer phase is directed into the aqueous liquid by pumping the first volume through the membrane.
7. The method according to claim 1 , wherein the membrane is substantially metallic.
8. The method according to claim 7 , wherein the membrane is wholly metallic.
9. The method according to claim 7 , wherein the membrane comprises nickel.
10. The method according to claim 1 , wherein the slot-shaped through holes have an aspect ratio of slot width to slot length of at least 1:2.
11. The method according to claim 1 , wherein the polymerizable monomer phase comprises at least one monomer selected from styrene, divinylbenzene, and methacrylate.
12. The method according to claim 1 , wherein the polymerizable monomer phase comprises divinylbenzene.
13. The method according to claim 1 , wherein the polymerizable monomer phase comprises a porogen.
14. The method according to claim 13 , wherein the porogen is an aliphatic alcohol.
15. The method according to claim 14 , wherein the aliphatic alcohol is isobutyl alcohol.
16. The method according to claim 1 , wherein the aqueous liquid comprises a viscosity modifier.
17. The method according to claim 16 , wherein the viscosity modifier is polyvinyl alcohol.
18. The method according to claim 1 , wherein the metallic membrane comprises nickel, the monomer phase comprises divinylbenzene and isobutyl alcohol and the aqueous liquid comprises polyvinylalcohol.