Design and synthesis of a two compartment micellar system based on the self-association behavior of poly(N-acylethyleneimine) end-capped with a fluorocarbon and a hydrocarbon chain

The synthesis, characterization, and association behavior of a new class of amphiphilic polymer surfactants are described. Living cationic polymerizat ion of 2 methyl-2-oxazoline was utilized to create a series of water solubl e polymer surfactants FPxLn, where F denotes a well defined fluorinated end group C8F17CH2CH2, P-x denotes the degree of polymerization and L-n a hydr ocarbon end group of variable length CnH2n+1, n = 6, 8,..., 18. The molecul ar weights and polydispersities of the polymers were determined by gel perm eation chromatography (GPC) in chloroform. H-1 NMR spectroscopy was used to calculate the number average degree of polymerization and the degree of en d group modification with the hydrocarbon chain containing termination agen t. The molecular weights and degree of polymerization corresponded closely to the values expected from the monomer/initiator ratio. The polydispersiti es were low, ranging from 1.15 to 1.20. The extend of end group modificatio n was calculated to be a minimum of 85% for all polymers. Fluorescence expe riments employing pyrene as a probe showed that these polymers form aggrega tes in water through self-association in the concentration range from 0.018 to 0.061. wt.-%. In addition, the micropolarity experienced by the peak ra tio I-1/I-3 in the vibronic fluorescence spectrum of pyrene above the cme u p to 1.0 wt.-% changed from hydrocarbon-like for FPL12, FPL14, FPL16 and FP L18 to fluorocarbon-like for FPL6 and FPL8, and intermediate. behavior for FPL10. Dynamic light scattering of FP25L16 showed single micelles at a conc entration of 0.50 wt.-% and 2.0 wt.-% with a hydrodynamic radius of R-h = 5 .5 and 6.7 nm, respectively. F-19 NMR experiments were applied for FP25L16 to study the aggregation behavior of the fluorocarbon: end group. T-2 relax ation experiments indicated that the degree of aggregation increased linear ly with polymer concentration. Moreover, the results of the T-2 relaxation experiments suggested the presence of pure fluorocarbon phases consistent w ith those found by fluorescence spectroscopy for FP25L16.