Aggregation Behavior and Application Properties of Novel Glycosylamide Quaternary Ammonium Salts in Aqueous Solution

Amidation of lactobionic acid with N,N-dimethylaminopropyltriamine was conducted to obtain N-(3'-dimethylaminopropyl)-lactamido-3-aminopropane (DDLPD), which was quaternized with bromoalkanes of different carbon chain lengths to synthesize double-stranded lactosylamide quaternary ammonium salt N-[N'[3-(lactosylamide)]propyl-N'-alkyl] propyl-N,N-dimethyl-N-alkylammonium bromide (C_nDDLPB, n = 8, 10, 12, 14, 16). The surface activity and the adsorption and aggregation behaviors of the surfactants were investigated via equilibrium surface tension, dynamic light scattering, and cryo-electron microscopy measurements in an aqueous solution. The application properties of the products in terms of wettability, emulsification, foam properties, antistatic, salt resistance, and bacteriostatic properties were tested. C_nDDLPB exhibited a low equilibrium surface tension of 27.82 mN/m. With an increase in the carbon chain length, the critical micellar concentration of C_nDDLPBD decreased. Cryo-electron microscopy revealed that all products except C₈DDLPB formed stable monolayer, multi-layer, and multi-compartmental vesicle structures in an aqueous solution. C₁₄DDLPB has the best emulsification performance on soybean oil, with a time of 16.6 min; C₁₄DDLPB has good wetting and spreading properties on polytetrafluoroethylene (PTFE) when the length of carbon chain is from 8 to 14, and the contact angle can be lowered to 33°~40°; C_nDDLPB has low foam, which is typical of low-foaming products; C₈DDLPB and C₁₀DDLPB both show good antistatic properties. C₈DDLPB and C₁₄DDLPB have good salt resistance, and C₁₂DDLPB has the best antimicrobial property, with the inhibition rate of 99.29% and 95.28% for E. coli and Gluconococcus aureus, respectively, at a concentration of 350 ppm.