Novel Polysaccharide Surfactants: The Effect of Hydrophobic and Hydrophilic Chain Length on Surface Active Properties

Abstract

A series of nonionic saccharide surfactants with an amide group linking hydrophilic saccharide segment to hydrophobic alkyl segment were synthesized and their surface active properties were determined. We examine the effects of hydrophobic and hydrophilic chain lengths on the surface active properties and correlate our results to structural differences in the saccharide surfactants.N-Alkylmaltonamides were synthesized with hexyl, octyl, decyl, dodecyl, and octadecyl alkyl segments andN-dodecyl aldonamides were synthesized with glucose, maltose, and dextran (DP = 9) saccharide segments. Increasing the alkyl chain length inN-alkylmaltonamides decreases the critical micelle concentration, and increases the efficiency of reducing water surface tension and emulsification ability, but the effectiveness in reducing water surface tension is about the same. Increasing the saccharide size inN-dodecyl aldonamides from glucose to maltose to dextran increases the critical micelle concentration, decreases the efficiency and effectiveness of reducing water surface tension, but has little effect on emulsification properties. We show that the size of the saccharide segment is important in determining the interfacial surface area occupied by the surfactant molecules. An octyl, decyl, or dodecyl maltonamide occupies about 40 Å2at the air/water interface, but this increases to 60 Å2when maltose is replaced by the larger dextran.