Studies On Synthesis And Properties Of Acyl Glucosamine And Hydroxyalkylated Glucosamine Surfactants

Chitin is an abundant natural organic resource which possesses unique characteristics, such as non-toxicity, harmlessness, good biocompatibility and good biodegradability. In recent years, more and more attention has been paid on the new kind of aminosugar surfactants which derived from chitin. In this paper, the synthesis and properties of acyl glucosamine and hydroxyalkylated glucosamine surfactants were studied.First, the hydrolysis of chitin in the concentrated hydrochloric acid solution was studied. The appropriate conditions for the preparation of glucosmine hydrochloride ( GAH ) from chitin are as follows: chitin powder dispersed in hydrochloride acid at 65℃, chitin-hydroloride ratio 1∶2 ( w/v ), temperature 95℃, time 75 min, decolored by activated carbon at 2.5 % -3.0 % ( w.t. % ) for 30 min, and GAH separated out in 95 % ( w.t.% ) ethanol. Under the above conditions, the yied of GAH is 70%. The structure of the aim product was characterized by infrared spectroscopic ( IR ) analysis and chlorine ion content analysis.Secondly, series of acyl glucosamine surfactants, such as octanoyl glucosamine, caprinoyl glucosamine, dodecyl glucosamine, myristoyl glucosamine and palmitoyl glucosamine were synthesized by reactions of fatty acid chloride with GAH. The synthesis of dodecyl glucosamine was studied in detail. The appropriate synthesis conditions of acyl glucosamine are as follows: mole ratio of GAH to fatty acid chloride 1.0∶1.1, mixture of 15 mL water and 15 mL acetone as reaction medium, pH 9～10, tempreture 6℃, and time 1.0 ~ 1.5 h. The structures of the aim products were characterized by IR analysis and nitrogen content analysis. Some fundamental physical and chemical properties and several functional properties of acyl glucosamine surfactants were studied. The experimental results showed that all the five acyl glucosamine surfactants are soluble in water and possess good surface activities; their critical micelle concentration ( cmc ) values are among 1×10-5 mol·L-1 ~ 1×10-4 mol·L-1, the minimum surface tension (γcmc) values are 35.27, 31.46, 28.83, 28.42, 32.32 mN·m-1 at 25℃, respectively. All of them have certain foaming ability and emulsifying property. As the length of hydrophobic carbon chain increasing, their solubility decreased, and surface activity, emulsifying abilitiy and foam ability, increas at first and then decrease.At last, hydroxyalkylated glucosamine surfactants——(2-hydroxy-3-dodecyl dimethyl quaternary ammonium) propyl glucosamine ( QA-GluN ) was synthesized by reaction of epoxypropyl dodecyl dimethyl ammomium chloride ( DTGA ) with GAH. The appropriate synthesis conditions of QA-GluN are as follows: mole ratio of GAH and DTGA is 1∶1.1, mixture of 40 mL isopropy and 15 mL water as reaction medium, temperature 55℃, and time 3.0 h. Under the above conditions, the yield of product is 72.6 %. Some fundamental physical and chemical properties and several functional properties of QA-GluN were studied. The experimental results showed that QA-GluN possesses good solubility and surface activity, certain emulsifying property and foaming capability. The cmc,γcmc, saturated adsorption amount (Γmax ) and saturated adsorption area ( Amin ) of QA-GluN at 25℃were calculated as 0.5 mmol·L-1, 25.9 mN·m-1, 2.61×10-6mol·cm-2, and 0.64 nm2, respectively. QA-GluN possesses good compatibility with cetyltrimethyl ammoniu chloride (1631), Tween 80, and dodecyl dimethyl betaine, respectively. The mixture of QA-GluN and sodium lauryl sulfate ( SDS ) becomes instable while the concentration of SDS increases to certain degree.