Synthesis Of Comb-like And Hyperbranched Polythioethers By Thiol-ene/yne Click Reaction And Their Antibacterial Properties

With the advantages of simple process,high efficiency,mild reaction conditions,and satisfied chemical selectivity,click chemistry has been widely used in polymer synthesis,material functionalization and so on.Thiol-ene/thiol-yne click addition is a kind of novel ones.Compared with the traditional azide-alkyne click chemistry,it has the advantages of free-toxic copper catalyst,simple purification procedure,being no effect on the reaction rate in presence of various functional groups.Therefore,thiol-ene/thiol-yne has been widely applied in the synthesis and functionalization of biomedical materials.Being of a large number,a wide range of distribution,and a strong reproductive ability,bacteria can induce a variety of diseases.Antibacterial agents with a high molecular weight have the good biological safety and excellent antibacterial activity.However,up to now,there are few high-efficiency synthetic strategies.In this work,we synthesized cationic comb-like and hyperbranched polythioethers through the thiol-ene/thiol-yne click addition.Their chemical structures and antibacterial activity had been characterized.Our work presented a new way for the polymer antibacterial agents.Firstly,vinyl-containing polythioethers with three different molecular weights were facilely synthesized via thiol-ene/thiol-yne click addition.After that,they were functionalized and turned to cationic polythioethers by subsequent thiol-ene and/or Menshutkin click addition.Their structures were confirmed by nuclear magnetic resonance spectrum(NMR)Fourier transform infrared spectroscopy(FTIR),and gel permeation chromatography(GPC)measurements.Thermal performance was tested by scanning calorimeter(DSC).The antibacterial activity was carefully measured using the bacteriostatic zone method.The results showed that the number average molecular weights(M_n)of three vinyl group-containing polythioethers were 1.31×10⁴,1.13×10⁴and9.42×10³ g mol^-1,respectively,as the feeding ratios of epoxy groups and amine groups were 1:0.51,1:0.525 and 1:0.55.Subsequently,the as-prepared three vinyl-polythioethers were functionalized by thiol-ene and/or Menshutkin click addition,offering two types of cationic polythioethers.The glass transition temperature(T_g)values of two types of cationic polythioethers were in the range of 16.67?17.25°C and-3.1?2.1°C,respectively.The size of antibacterial zone and minimum inhibitory concentration(MIC)were used to evaluate the antibacterial activity of the two as-synthesized cationic polythioethers.For Staphylococcus aureus(S.aureus)and Escherichia coli(E.coli),the MIC values of ammonium hydrochloride polythioethers were 4.88?g m L^-1,and the MIC values of quaternary ammonium ones were 4.88 and 2.44?g m L^-1,respectively.It shows that the comb-like polythioethers with quaternary ammonium salt functional groups have a better antibacterial activity on E.coli,compared with those with ammonium hydrochloride groups.Secondly,we synthesized a series of alkynyl group-containing polythioethers via the thiol-yne click addition.Subsequently,they were functionalized and turned to cationic polythioethers by thiol-yne click addition.Their structures were confirmed by NMR,FTIR,and GPC measurements.Thermal performance was tested by DSC.The antibacterial activity was measured using the bacteriostatic zone method.The results showed that M_n of three alkynyl group-containing polythioethers were 4.15×10³,5.37×10³ and 6.69×10³ g mol^-1,respectively.After that,the as-prepared three alkynyl-polythioethers were functionalized by thiol-yne click addition,offering the cationic comb-like polythioethers.The T_g values of cationic polythioethers were in the range of 31.42?36.22°C.For S.aureus and E.coli,the MIC values of cationic polythioethers were 2.44,2.44 and 1.22?g m L^-1,respectively.Finally,three types of hyperbranched polythioethers were facilely synthesized via thiol-yne click addition by control of the amount of sodium methoxide.Their structures were confirmed by NMR,FTIR,and GPC measurements.The degree of branching(DB)values were calculated to be 0.86,0.78 and 0.73.With increasing of the DBs,the T_g values of the as-prepared cationic hyperbranched polythioethers were-4.5,37.3,and 52.9°C,respectively.The cationic polythiothers exhibited good antibacterial activity,such as,for S.aureus,the MIC values were 6.24,3.12 and 1.56?g m L^-1;for E.coli,the MIC values were 1.56,1.56 and 0.78?g m L^-1 successively.The results showed that,for E.coli,the hyperbranched polythioethers with ammonium hydrochloride groups exhibited a better antibacterial activity compared with those with quaternary ammonium salt groups.