EMULSIFICATION OF POLY(ETHYLENE GLYCOL) IN THERMOPLASTIC ELASTOMERS BY USING POLYBUTADIENE-BLOCK-POLY(ETHYLENE OXIDE) DIBLOCK COPOLYMERS ASSTABILIZERS - 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 disper sed liquid phase of poly(ethylene glycol) (PEG) were prepared by start ing from an emulsion of PEG dispersed as small droplets in a solution of SEBS in methylcyclohexane. A polybutadiene-block-poly(ethylene oxid e) block copolymer is used as emulsifier and stabiliser for these emul sions. The particle size of the dispersed PEG phase, in the emulsion, and in the final film obtained by solvent evaporation could be adjuste d as a function of the block copolymer concentration. The morphology o f the material was studied by scanning electron microscopy (SEM) and p ulsed field gradient (PFG) NMR. From the diffusion coefficients determ ined 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 th e rubber matrix micelles and aggregates (polymolecular micelles) which are able to ''solubilize'' a given fraction of PEG.