Linear-dendritic nonionic poly(propylene oxide)-polyglycerol surfactants

A new type of linear-hyperbranched surfactant has been prepared by anionic ring-opening multibranching polymerization of Glycidol onto an end-functional poly(propylene oxide) (PPO) macroinitiator. A hyperbranched, highly hydrophilic polyglycerol block is obtained as the polar segment of the structure. Molecular weights of the nonionic amphiphiles obtained were in the range of 390 to 8,600 g/mol. For comparison. initiators bearing a C16 alkyl chain have also been employed. Furthermore, hyperbranched polyglycerol homopolymers were investigated with respect to amphiphilic properties. All linear-dendritic amphiphiles have been characterized by SEC, DSC. C-13 and H-1 NMR spectroscopy. A fluorescence-probe technique based on diphenyl hexatriene (DPH) as probe molecule was employed to determine the CMC (critical micelle concentration) of the samples in water. CMCs varied from 7.5x10(-6) to 1.7x10(-3) M and were found to depend on the copolymer architecture and the hydrophilic/hydrophobic balance. Measurements at pH 6.75 and 3.00 revealed an increase of the CMC by a factor of 10 for the amine containing copolymers upon lowering of the pH. (C) 2003 Elsevier Science Ltd. All rights reserved.