Synthesis And Antibacterial Ability Of Novel Polyisocyanide Quaternary Ammonium Salts

Polymer quaternary ammonium salts have essential research significance and value in basic research and material application fields due to their high antibacterial activity,good processing performance,variety of types,and durability.Palladium catalyst cat.a and cat.b which can initiate living/controlled polymerization of phenyl isocyanides,were separately synthesized through the complex reactions of Pd?PEt₃?₂Cl₂ with phenylacetylene and1,3,5-triethynylbenzene,respectively.Phenyl isocyanide monomer1 with a n-butyl side chain and monomer2 with a 4-chloro-1-butyl side chain were successfully designed and synthesized.Cat.a initiated the living/controlled polymerization of monomer2 to produce a serie of linear polyisocyanates?L-P-2m“m”represent the polymerization degree?containing 4-chloro-1-butyl side groups with different polymerization degree and narrow distribution.Two star-shaped polyisocyanates?S-P-2n,“n”represent the polymerization degree?were prepared by the living/controlled polymerization of monomer2 initiated by cat.b.L-P-2mandS-P-2nweremodifiedbyN,N-dimethylbenzylamine,N,N-dimethyl-n-butylamine,N,N-dimethyl-n-octylamine and N,N-dimethyldodecylamine to produce the corresponding linear polyisocyanides quaternary ammonium salts?P-QASs?L-PRQAS-2m?R represent benzyl,n-butyl,n-octyl and dodectl,m=50 or 100?,as well as two star structure P-QASs(S-POcQAS-2₅₀,S-POcQAS-2₁₀₀).The chemical structures of the synthesized compounds were systematically characterized by nuclear magnetic resonance,infrared spectroscopy,and etc.The antibacterial activity of the synthesized P-QASs on E.coli and S.aureus were evaluated by the minimum inhibitory concentration?MIC?method.As a result,all the prepared P-QASs showed good antibacterial activity against both E.coli and S.aureus.When the L-P-QASs has the same polymerization degree,the order of the antibacterial activity of the P-QASs on E.coli and S.aureus was L-POcQAS-2n>L-PBuQAS-2n>L-PBnQAS-2n>L-PDBQAS-2n?n=50,100?.When P-QASs took the same side chain,the antibacterial activity against E.coli and S.aureus reduced more or less with the increase of the molecular weight of the main chain.The P-QASs of star structure showed the better antibacterial activity on E.coli and S.ureus than the corresponding linear structure P-QASs.The MIC of the star structure S-POcQAS-2₅₀ against E.coli and S.aureus was 17 ug/mL and 20 ug/mL,respectively,the MIC of S-POcQAS-2₁₀₀ on E.coli and S.aureus was 19 ug/mL and 17ug/mL,respectively.This is probably due to the fact that the star-shaped structure of the polymer increases the cation density of the P-QASs and increases the water solubility of the corresponding P-QASs.