Self-aggregation of dendritic poly(benzyl ether)-poly(acrylic acid), an amphiphilic block copolymer, studied by 1 H NMR

Abstract

The dynamic properties of the micelles of a novel synthesized amphiphilic block copolymer, dendritic poly(benzyl ether) -poly(acrylic acid) (Dendr.PBE-PAA), formed in aveous solutions were studied by the H-1 self-diffusion coefficient, relaxation measurements and 2D nuclear Overhauser enhancement spectroscopy. The experimental results show that Dendr.PBE-PAA molecules self-aggregate in aqueous solution. The dynamic properties of the Dendr.PBE-PAA micelles vary with their total concentration in the solution. The motion of the molecules in the micelles of a concentrated solution is more restricted than that in a less concentrated one. The main chains of PAA are densely packed in the surface layer of the hydrophobic core with the carboxyl side chain pointing to the aqueous medium and the hydrophobic phenoxy rings stay in the interior. The self-aggregate becomes larger as the degree of polymerization of PAA increases. However the phenoxy rings situated in the interior of the hydrophobic core become more loosely packed. n-Hexadecane is solubilized in the micelles. The optimal position of n-hexadecane is between the phenoxy rings next to the PAA chains.