Synthesis And Properties Of Inulin Quaternary Ammonium Salts-Cationic Surfactants

A series of inulin quaternary ammonium salt were synthesized from inulin, epichlorohydrin and N,N-dimethyldodecylamine(N,N-dimethyltetradecylamine,N,N-dimethylhexadecylamine, N,N-dimethyloctadecylamine) via two methods.Meanwhile,the structure of the products was characterized by IR analysis and the degree of substitution(DS) of the products was analyzed by full-automatic azotometer.Then,the general physical-chemical properties,such as surface activity,foam and emulsifying ability,mixing ability and solubility were studied.Finally,the moisture absorption and retention properties and the preservation effect for cucumber were investigated.Aiming to get higher degree of substitution(DS) of the product,several experimental conditions were optimized,including raw material composition,amount of base,the duration time in base,reaction temperature and reaction time.The optimized conditions are as follows: the ratio of n(inulin):n(epichlorohydrin):n(N,N-dimethyldodecylamine) is 1:3:3,the amount of base is 0.3 g,the duration time in base is 40 min,reaction temperature is 70℃,and reaction time is 7 hours,DS achieves 1.44 when it reaches the optimized condition.The surface tension and cmc value of dodecyl inulin quaternary ammonium salt were 31.48 mN/m and 2.29E-4 mol/L respectively,which meant that this kind of surfactant had good surface activity.At the same time,the micelle thermodynamic parameters revealed that the micellization process was spontaneous,and gained heat in the temperature range of 298K and 313K.The absolute value of -Tâ–³S_m⁰ was larger than that ofâ–³H_m⁰,indicating the contribution of entropy to free energy.The surface properties calculation of the mixture of inulin quaternary ammonium salt and sodium dodecyl sulphate(SDS) showed that there was strong synergic effect in the mixture.The surface chemical performance of the mixture was significantly better than that of the monosurfactant system.The surface tension and cmc of the mixture is 25.60 mN/m and 0.46×10^-4 mol·L^-1 respectively when the ratio of n(inulin quaternary ammonium salt):n(SDS) is 8:2.The foaming ability and emulsifying ability of inulin quaternary ammonium salt were also studied.The initial foam volume of inulin quaternary ammonium salt(DS=0.8) is 78 mL while the final foam volume is 76 mL with the stability coefficient is 0.97,meanwhile,the emulsifying time is 187 min for paraffin liduid.Finaly,the moisture absorption,moisture retention properties and the preservation effect for cucumber of the inulin quaternary ammonium salt were investigated.The moisture absorption ratio of inulin quaternary ammonium salt(DS=0.8) is 27.5%after 48 h when the relative humidity(RH) is 81%,and the moisture retention ratio could reach 75.7%after 48 h when RH is 4.3%.The preservation effect for cucumber coated with inulin quaternary ammonium salt can slow the loss of total chlorophyll and vitamin C during storage.The content of vitamin C and chlorophyll of the cucumber coated with inulin quaternary ammonium salt(DS=0.8) is 0.193 mg/g and 0.326 mg/g after two days while the content of vitamin C and chlorophyll is 0.145 mg/g and 0.231 mg/g respectively when the cucumber without coating.