A process for prepg. a water sol. polymer comprises: providing a polymn. reaction mixt. comprising one or more polymerizable ethylenically unsatd. monomers; polymg. the ethylenically unsatd. monomers; and adding to the reaction mixt. during polymn. one or more chain branching agents (e.g., methylenebisacrylamide) either continuously or semi-continuously, the semi-continuous addn. further comprising at least two discrete addns. The polymers, typically acrylamide-based, have improved flocculating and dewatering properties. The polymer is useful in solid/liq. sepns. such as flocculants and coagulants in wastewater treatment applications, and as thickening agents. [on SciFinder (R)]