Precise Determination of the Hydrophobic/Hydrophilic Junction in Polymeric Vesicles

In the present paper, we present a complete characterization of the propylene sulfide-ethylene glycol triblock copolymers (PPS-PEG) at a mol. level, and as lyotropic aggregates, with the precise localization of the hydrophilic/hydrophobic border of their vesicles through a complete assignment of 1H and 13C NMR spectra. The assignments here reported for the PPS main chain correct a partially erroneous assignment reported previously, where the presence of diastereotopic protons was not taken into account. In this study, we used multi dimensional NMR measurements for the 1H and 13C assignments (two-dimensional NMR studies of the conformation and mol. dynamics in colloidal aggregates are relatively common) and 1H CPMG (Carr-Purcell-Meiboom-Gill) expts. for the detn. of the transverse relaxation times [T2's, inversely proportional to the full width at half-height (fwhh) of the peaks], which are well-known for relating mol. mobility in an inversely proportional fashion. We have used this feature for discriminating a hydrophobic domain (bulk PPS, viscous phase with short T2's) from a water-swollen, soln.-like one (highly mobile PEG with longer T2's). [on SciFinder (R)]