PFG NMR study of polymer and solubilizate dynamics in aqueous isotropic mesophases of some poloxamers

The self-diffusion of the polymer and oil (i.e., tert-butylbenzene) compone nts in aqueous ternary cubic liquid crystalline (clc) mesophases formed by three different Pluronic triblock copolymers (i.e., P94, F68, and F127) has been investigated using pulsed-field gradient (PFG) NMR. For the polymer c hains, the diffusion has been compared to that determined in corresponding aqueous binary (without oil) de mesophases and micellar solution phases. Th e polymer chain diffusion is Fickian (i.e., Gaussian) in the micellar solut ion state and becomes anomalous in the clc mesophases. A pronounced departu re from a single-exponential spin-echo attenuation of the polymer chains in the de mesophases is observed. The self-diffusion of the oil component in the ternary de mesophases is Fickian. Compared to the self-diffusion of the pure oil at the same temperature, it is found that the diffusion is reduce d by a factor of 10(3) in the de mesophases. This clearly demonstrates that the de mesophases consist of closed aggregates with the oil solubilized in the micelles. A possible scenario for the observed polymer chain and the o il diffusion behavior is discussed, based partly on PFG NMR results obtaine d from a binary aqueous de sample of the surfactant dodecyl trimethylammoni um chloride (DOTAC).