Synthesis,Characterization And Antifungal Activities On Rhizoctonia Solani Of Polymeric Quaternary Ammonium Salt

Rice sheath blight which was caused by Rhizoctonia solani(R.solani)is one of the three major diseases in rice production.R.solani can overwinter in the form of sclerotia,and the sclerotia have a hydrophobic outer layer and inner layer composed of a large number of mycelium.Conventional pesticides are difficult to penetrate into the inner layer of sclerotia.The control of R.solani sclerotia is a difficult problem in rice sheath blight control due to the strong ability to survive of R.solani sclerotia.Compared with the corresponding quaternary ammonium salt monomers,the polymeric quaternary ammonium salts has higher antimicrobial activities and lower biotoxicity.And polymeric quaternary ammonium salts can obtain the best antibacterial activity by adjusting the structure.In this paper,an amphiphilic polymeric quaternary ammonium salt was proposed.The amphiphilic polymeric quaternary ammonium salt can effectively adsorb and permeate into the sclerotia,and inhibit the mycelium.On this basis,the relationship between the structure of linear hydrophilic polymeric quaternary ammonium salt and antifungal activities and environmental toxicity was further discussed.The main work of this paper consists of three parts:1.A series of acrylate polymers containing quaternary ammonium salts(PDMAEMA-BC)with different molecular weights were synthesized via atom transfer radical polymerization(ATRP).The effects of molecular weight of PDMAEMA-BC on the antimicrobial activities against Escherichia coli(E.coli),Staphylococcus albus(S.albus),Candida albicans(C.albicans),R.solani and Fusarium oxysporum f.sp.cubense race 4(Foc4)were systematically assessed.The results indicated that the optimal antimicrobial activities were achieved when the polymerization degree of PDMAEMA-BC is moderate(about 16).2.Based on the synthesis of PDMAEMA-BC,a series of polydimethylsiloxane-polymethacrylate block copolymers containing quaternary ammonium salts(PDMS-b-QPDMAEMA,labeld as Sn Qm)were synthesized via anionic ring-opening polymerization and ATRP.The molecular weights of QPDMAEMA chain were designed as 5 k Da and the molecular weights of PDMS chain were designed as 2 k Da to 10 k Da.The abilities of the PDMS-b-QPDMAEMA to adsorb and permeat the R.solani sclerotia and inhibit the germination of R.solani sclerotia were investigated.We found that the PDMS-b-QPDMAEMA can obtain better abilities to adsorb and permeat the sclerotia and inhibition effect on R.solani sclerotia germination when the molecular weights of QPDMAEMA chain and PDMS chain were about 5 k Da.3.A series of linear hydrophilic cationic polymers were synthesized.And the antifungal activities,antifungal mechanism and environmental toxicity were assessed.The results indicated that the linear hydrophilic cationic polymers with low toxicity and high selectivity can be obtained by adjusting the hydrophobic-hydrophilic balance.