Submicron-sized P(St-NaSS) latexes were prepared

via

a semi-continuous emulsion copolymerization of styrene (St) and sodium styrene sulphonate (NaSS) in the presence of anionic surfactant

in which NaSS aqueous solution and St were separately dropwise charged into the polymerization system at the same time. The hydrodynamic diameter of the latex particles was measured by dynamic light scattering (DSL) method

and the NaSS unit content of the purified copolymer by water extraction was calculated based on the elementary analysis. Results showed that the copolymerization could be performed smoothly with the monomer conversion more than 96% in the absence of crosslinker

and PNaSS homopolymer could be removed from the latex product by water extraction for 28 h. The weight loss in the water extraction tended to decrease and the NaSS unit content of the purified copolymer tended to increase with the increase of monomer feeding time

and both of them increased with the increase of NaSS/St mole ratio in the charge. The introduction of divinyl benzene (DVB) could decrease the weight loss in the water extraction and increase the NaSS unit content of the purified copolymer. When 25/75 mole ratio of NaSS/St and 11 mol% DVB of total NaSS and St were used in the recipe

and the monomer feeding time was 3 h in copolymerization

the NaSS unit content of the purified copolymer reached 7.31 mol%.