Emulsification of poly(ethylene glycol) in thermoplastic elastomers by using polybutadiene-block-poly(ethylene oxide) diblock copolymers as stabilisers. Determination of the liquid phase mobility by pulsed field gradient NMR

Polymeric film materials comprising a continuous elastomer phase of a styrene-hydrogenated diene thermoplastic elastomer (SEBS) and a dispersed liquid phase of poly(ethylene glycol) (PEG) were prepared by starting from an emulsion of PEG dispersed as small droplets in a solution of SEBS in methylcyclohexane. A polybutadiene-block-poly(ethylene oxide) block copolymer is used as emulsifier and stabiliser for these emulsions. The particle size of the dispersed PEG phase, in the emulsion, and in the final film obtained by solvent evaporation could be adjusted as a function of the block copolymer concentration. The morphology of the material was studied by scanning electron microscopy (SEM) and pulsed field gradient (PFG) NMR. From the diffusion coefficients determined by PFG NMR it is demonstrated that a part of the block copolymer, in addition to its stabilisation effect, has a tendency to form in the rubber matrix micelles and aggregates (polymolecular micelles) which are able to "solubilize" a given fraction of PEG.