| Popis: |
Two polymerizable surfactants (surfraers), namely, monododecyl itaconate (MDDI) and monocetyl itaconate (MCI), were synthesized by reacting itaconic anhydride with 1-dodecanol and cetyl alcohol,respectively. A series of uncross linked and crosslinked surface-carboxylated latexes were prepared from styrene and styrene-divinyl benzene, respectively, using varying amounts of these two surfraers. The latexes were characterized by gravimetry, dynamic light scattering, and conductometric titration in order to obtain the conversion, particle size distribution, and concentration of surface carboxyl groups, respectively. The size of latex varied between 41-72mn and was seen to depend inversely on the surfmer concentration. In the case of the soluble polystyrene latexes, solution H-1 NMR spectr aprovided conclusive evidence for surfmer incorporation into the polymerchain. Comparison of the incorporation levels determined by NMR with the surface carboxylic acid concentrations in the latexes, determined by conductometric titrations, revealed that the majority of the surfraers, as ancticipated, were present on the latex surface. The study of the stability of the latexes to varying salt concentrations clearly demonstrated that the smaller-size latexes having higher surface carboxyl group density exhibited far improved stability when compared with the larger-size ones having lower surface carboxyl group density. Similarly, enhanced freeze-thaw stability was also observed for the smaller-size latexes. MCI-based latexes exhibited marginally improved stability compared with those prepared using MDDI, which again seems to be because of the higher surface functional group density in the former. |
