Synthesis and flocculation performance of graft and random copolymer microgels of acrylamide and diallyldimethylammonium chloride

Graft (from linear homopolymers) and random (from a linear random copolymer ) copolymer microgels of diallyldimethylammonium chloride (DADMAC) and acry lamide were synthesized via a free-radical mechanism using a ii-radiation t echnique. These copolymer microgels were evaluated as flocculants on a mode l dilute TiO2 colloid suspension using a turbidimeter and a disc centrifuge photosedimentometer, and their performances were compared with the linear homopolymers and their blends. It was found that microgels produced after a n appropriate irradiation time showed improved flocculation behavior over t heir nonirradiated linear counterparts. The graft microgels performed bette r than the corresponding random microgels. For a gamma-radiation dosage of 100 krad/h, the graft microgels obtained by irradiating a 30% DADMAC: (by w eight) homopolymer blend for 3 h showed the maximum reduction in the relati ve turbidity of the TiO2 suspension as well as the largest fraction of larg er particles flocculated.