Solution Properties of Amphiphilic Telomers with Multiple Sugar Chains and Terminal Alkyl Chain

Abstract

Amphiphilic telomers with multiple sugar chains and a terminal undecyl or heptadecyl chain (i.e., C_nAm-mGEMA, where n and m represent alkyl chain lengths of 11 or 17 with a degree of polymerization of 2.0 or 3.0 for glucosyloxyethyl methacrylate (GEMA) units, respectively) were synthesized via monomeric radical telomerization in the presence of 2-aminoethanethiol hydrochloride. Surface tension, pyrene fluorescence, and dynamic light scattering were measured to characterize the solution properties of the synthesized telomers. In addition, the effects of alkyl chain length and degree of polymerization of hydrophilic GEMA units on the measured properties were evaluated by comparison with those of conventional polyoxyethylene dodecyl ether nonionic surfactants. C_nAm-mGEMA telomers exhibited higher critical micelle concentration (CMC) values than polyoxyethylene dodecyl ether surfactants with similar number of hydrophilic groups did. The synthesized telomers are highly efficient in reducing the surface tension of water, despite the relatively large hydrophilic structures within the sugar units (GEMA). A unique behavior was observed in that adsorption at the air-water interface and solution aggregation occurred simultaneously at a concentration below CMC (as determined by the surface tension method). This suggests that aggregate formation occurs readily in solution along with the adsorption at the interface because of strong attractive interactions between multiple sugar GEMA chains. Further, aggregates formed by C_nAm-mGEMA telomers differ depending on the number of sugar chains, i.e., an increase in the degree of polymerization of the telomers increases the size of the aggregates. This indicates that it is easier for telomers with more sugar GEMA chains to form large aggregates due to the interactions between their hydroxyl groups.