Relative Importance of the Effects of Seed and Feed Stage ...

364 Krishnan et al.
Figure 1.
1 H-NMR spectrum of water-soluble species in the latex.
1 H-NMR spectra of the solids in the serum showed that there are
negligible amounts of SDS and unreacted NMA in the serum of the final
latex. Figure 1 shows the spectrum for the water-soluble species in the
serum of the latex obtained from Run 4 (cf. Table 2). The serum was
separated from the latex by ultracentrifugation. H 2 O was evaporated (at
room temperature) from the serum by bubbling nitrogen into a glass vial
containing the serum. The solids remaining in the vial were then
redissolved in D 2 O. On comparison of this spectrum with that reported in
the previous paper (Krishnan et al., 2003), it is observed that the peaks
corresponding to SDS are less pronounced in the former. This is expected
because of the lower concentration of SDS in the latexes prepared using
the recipe in Table 1, than that in the latexes of the previous paper
(Krishnan et al., 2003).
For the comparison of the effect of agitation on water-soluble polymer
formation, we use the values of the total amount of water-soluble species,
M ws obtained using Eq. 3. All other species in the serum (SDS, KPS,
NaHCO 3 , any unreacted NMA) are expected to be in the same amounts in
the serum for the different latexes, since the dilution of the latexes (for
ultracentrifugation) was the same. The dependence of the amount of SDS in
the serum, on the total surface area of the particles in the latex, is not
expected to alter the results significantly.
M ws ¼ M tot f ws ð3Þ