**3.1 Quaternary ammonium**

There are numerous antimicrobials suitable for immobilization on polymer surfaces. Quaternary ammonium compounds seem attractive because their target is primarily the microbial membrane and they accumulate in the cell driven by the membrane potential. To maximize efficiency, quaternary ammonium compound is used as monomeric link in the polymeric leash and poly(4- vinylpyridine) (PVP) is usually selected as the carrying polymer. Tiller et al. showed that the surfaces of commercial polymers treated with *N*alkylated PVP groups were lethal on contact to both Gram-positive and Gram-negative bacteria, and it was also shown that *N*-alkyl chain of six carbon units in length was the most effective. In recent years, trialkyl ammonium chlorides have been reported to possess germicidal effect in dilute aqueous solutions. (Yao et al, ,2008)

Kumar et al showed that mutual radiation grafting of vinylbenzyltrimethylammonium chloride (VBT ) onto cotton cellulose is an effective method to incorporate anti-bacterial property onto the cotton cellulose matrix.(Kumar et al, 2005) Shao et al showed that, a novel quaternary ammonium salt, which contains both perfluoroalkyl group and diallyl groups, should be suitable a finishing agent for providing the fabrics with barriers against microorganisms, water, oil, soil and blood. Moreover, the introduction of diallyl groups into the quaternary ammonium salt not only can enhance the antimicrobial activity, but also extend its application fields. It can be applied in two categories of antimicrobial finishes: one category is part of the fiber-forming process and the other category is the one incorporated in the finishing process. It can also be used as a perfluoroalkyl-containing monomer in the polymer field, which is a convenient method incorporating perfluoroalkyl chain in the polymer. (Shao et al, 2003)
