Preparation Of Quaternary Ammonium Salt/Phosphonium Salts Cationic Starch Graft Copolymers

Starch is an environmental protection, renewable and biodegradable natural polymermaterials. As petroleum supplies dwindle and become less reliable, starch takes onnew proportions as an abundant source of basic industrial chemicals. However, nativestarch has limited usage due to its in herent weakness of hydration, swelling andstructural organization. In order to remove these limitations and enhance theirviscosity, texture and stability, starch and its derivatives are generally modified bychemical, physical and biotechnological methods. Among them, starch modifications,by grafting vinyl monomers on to itself and then polymerization initiated either by achemical free radical initiator or by high energy irradiation have largely improved itshydrophilicity, hydrophobicity and polyelectrolyte nature. The grafting is achieved byfirst generating free radicals on starch backbone and then these radicals’ serveasmacro initiators for vinyl monomers. Several cationic starch graft copolymers wereprepared by a chemical free radical method and gamma irradiation in this project.They are cationic starch based hydrogels, Starch grafted acrylamide together withallyl triphenyl phosphonium bromide copolymers and Starch grafted acrylamidetogether with Tributyl-3-[(and4-)vinylbenzyl] phosphonium chloride. Thecopolymerization and application of starch graft copolymers were also studied andthe details as follows.(1) Cationic starch-based hydrogels were synthesized by simultaneously irradiatingstarch, acrylamide (AM), dimethyl diallyl ammonium chloride (DMDAAC), andN,N’-methylenebis acrylamide (MBA) in aqueous solution. A mechanism forhydrogel formation was proposed, and the product was characterized by FTIR and1HNMR techniques. The equilibrium swelling ratio of the hydrogels progressivelydecreased with increased absorbed dose at a fixed starch/AM/DMDAAC/MBA ratioof6:9.8:4.2:1.6. Meanwhile, the hydrogels showed similar shrinking behaviors withincreased absorbed dose. At a fixed starch/AM/DMDAAC weight ratio of6:9.8:4.2and fixed gamma irradiation of3kGy, equilibrium swelling ratio decreased with increased amount of crosslinking agent.(2) Starch/acrylamide/allyl triphenyl phosphonium bromide (St/AM/TP) copolymerswere synthesized by simultaneous gamma irradiation and characterized by FTIR and1H NMR techniques. Moreover, their antibacterial activities against Staphylococcusaureus were explored by the viable cell counting method in sterile distilled water. Theresults show that cationic degree (CD) of St-g-(AM-co-TPBC) copolymer wasgradually increasing with the increase of absorbed dose, monomer amount increasewill make product CD value increases, a glut of monomer amount, CD value nolonger increases;3kGy absorbed doses, appropriate ratio of monomers was m (St): m(AM): m (TPBC)=6:8.4:5.6, maximum CD was0.21, dosage of50mg/L, thecontact time for30min, sterilization rate for staphylococcus aureus was99.72%.(3) A cationic polymer was synthesized by graft copolymerization of corn starch withAcrylamide and Tributyl-3-[(and4-)vinylbenzyl] phosphonium chloride in aqueoussolution, and ammonium persulfate-sodium bisulfate as initiator. The grafting ratio(G), grafting efficiency of monomers (E) and yield of starch copolymers (Y) werestudied. The effects of the acrylamide concentration and monomer ratio on cationicdegree (CD) and reaction efficiency (RE) were discussed. The results showed that theCD and G of starch-grafted copolymers reached a maximum of0.21and98%,respectively, when the ratio of acrylamide and Tributyl-3-[(and4-)vinylbenzyl]phosphonium chloride is1.5. Furthermore, starch grafted copolymer was structurallycharacterized by FTIR, TG, XRD and SEM.