Abstract
Polymer particles were successfully prepared by immersion precipitation using micromixer and the effects of microchannel size of the micromixer, flow rate of fluid and solvent on the formation of particle were investigated. Polymer dispersion was obtained by micromixing an aqueous surfactant solution with a solution of the polystyrene in organic solvent. Some kinds of micromixers, IMM, YM-1 and YM-2 were used. The microchannel size of IMM, YM-1 and YM-2 was 40µm, 400µm and 400µm, respectively. A microdevice with the double pipe structure, which microchannel size was about 1500µm, was also used. An aqueous solution containing diisooctyl sodium sulfosoccinate (AOT) was used as nonsolvent. As solvent, tetrahydrofuran (THF) with low mutual affinity with water, N,N-dimethylacetoamide (DMAc) with middle affinity and N,N-dimethylformamide (DMF) with high affinity were used. Using all microdevices, polystyrene particle was formed without clogging of microchannel. The size of particle was dependent on the width of the microchannel of the micromixer. In the cases of THF and DMAc with the low affinity with water, the particle size was increased with an increase of total flow rate. This result suggested that the segment size of water and polymer solution also affected the particle size. The particle size was possible to control in the range from 150nm to 10 m by changing the micromixer, the total flow rate. It can be expected that this method of polymer particles will be used for the evaluation of the mixing performance of micromixers.
