Chemistry

Taste, Then Season

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Science  21 May 2004:
Vol. 304, Issue 5674, pp. 1079
DOI: 10.1126/science.304.5674.1079d

In dispersion polymerization, initiators, stabilizers, and monomer are all combined in one pot, and, as the ingredients are cooked, the product polymer drops out of solution in the form of particles with diameters of 1 to 15 μm. The reaction pathway consists of a fast, finicky nucleation stage, followed by a slow, simmering growth stage. This method is good for producing a single uniform distribution of particles, but it is difficult to make the particle size in one batch the same as in the next and to maintain a narrow distribution of particle size when co-monomers or cross-linking agents are included.

Song et al. decided to wait to add the flavoring agents until after the nucleation stage. By varying the amount of styrene monomer added in the second stage, they were able to vary the particle size without broadening the size distribution. They also were able to add up to 3% of a dye comonomer or to create cross-linked particles without running into the problems caused by particle coagulation, and they could even add comonomer and cross-linking agents at the same time. —MSL

J. Am. Chem. Soc. 10.1021/ja048862d (2004).

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