An excellent antibacterial cotton fiber/QAS copolymer was synthesized by a two step method. Dimethyl amino ethyl methacrylate (DMAEMA) was first grafted onto the surface of cotton fiber using ceric ammonium nitrate as the initiator

followed by quaternization with alkyl bromide agents. The optimum grafting conditions were found as following: the concentration of DMAEMA and initiator were 10%(φ) and 20 mmol/L

respectively; the reaction time

solution pH and reaction temperature were 5 h

1~1.5 and 45 ℃

respectively. Moreover

it was found that the type of solvents had a great effect on the quaternization of grafted DMAEMA

and the best solvent was acetone. The antibacterial activity of the cotton fiber/QAS copolymers depended on the grafting ratios of antibacterial monomers on the cotton fiber. Furthermore

the alkyl chain length of QAS substitution had a significant effect on the antibacterial performance. The grafted DMAEMA cotton fibers quaternized by using mixture of butyl bromide and dodecyl bromide possessed better antibacterial performance than that with butyl bromide alone.