Surface behavior and micelle morphology of novel nonionic polyurethane bolaform amphiphilic block copolymers

A novel series of nonionic bolaamphiphiles—polyurethane amphiphilic block copolymers were synthesized by addition polymerization. Their chemical structures were characterized using FTIR and ¹H-NMR spectra. The critical micelle concentration was determined by surface tensiometer and UV-vis absorption spectra. The surface behaviors of copolymers at air/water interface were also investigated including the effects of concentration, molecular structure, electrolytes, and rest time. The results show that these bolaform polyurethane amphiphilic block copolymers exhibited excellent surface activity: PU₃₄ could attain surface tension as low as 35.6 mN m⁻¹. According to the images of Transmission Electron Microscopy (TEM), the copolymers could self-assemble star-like aggregates comprised of hydrophobic block PPO surrounded by hydrophilic block PEO. Moreover, variation of concentration, the weight fraction of the hydrophilic block (f_phil), and the molecular weight of the copolymers could lead to the transformation of micelle (or premicelle) morphology. This provides a new and simple way to obtain nanoparticles with control over structure on the nanometer scale.