A gypsum composition containing a sulfonate-containing comb-branched
copolymer is disclosed. The sulfonate-containing comb-branched copolymer
comprises recurring units of a polyether macromonomer, an acrylic
monomer, and a sulfonate monomer. The sulfonate-containing comb-branched
copolymer not only increases the fluidity of gypsum slurry but also has
reduced retardation on the gypsum setting.