The effect of two different monomer addition strategies on the chemical composition distribution of the copolymer formed by the (seeded) semicontinuous emulsion copolymerization of styrene and methyl acrylate has been investigated. 1. The addition of a mixture of the monomers at a constant feed rate results in a homogeneous copolymer, provided that extremely long process times are used (starved conditions). When not starting from a seed latex, aqueous phase polymerization was observed at low feeding rates. When using a seed latex, aqueous phase polymerization appeared to be negligible. 2. In order to achieve an optimal monomer addition pattern, a pragmatic approach is presented. An optimal monomer addition profile was calculated from accurate monomer partitioning data using a short iteration procedure. Gradient high performance liquid chromatography (HPLC) was successfully applied as a rigorous test of the homogeneity of the copolymer formed. The information obtained contains much more detail than in the case of using differential scanning calorimetry of 1H NMR. In contrast to 1H NMR that provides only average cumulative chemical compositions, the complete chemical composition distribution can be obtained by means of HPLC.
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Doremaele et al. (1992) studied this question.
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