LIQUID POLYETHYLENE-GLYCOL DISPERSED IN A POLY(STYRENE)-B-POLY(ETHYLENE BUTYLENE)-B-POLY(STYRENE) ELASTOMER - DETERMINATION OF MORPHOLOGY AND MOLECULAR MOBILITY BY LIGHT AND ELECTRON-MICROSCOPY AS WELL AS NUCLEAR-MAGNETIC-RESONANCE SELF-DIFFUSION AND T-2 MEASUREMENTS/

An emulsion of liquid polyethylene glycol (PEG) in a rubbery (styrene) -b-poly(ethylene/butylene-b-poly(styrene) (SEBS) matrix was prepared u sing a poly(butadiene-b-poly(ethylene oxide) (PB-b-PEO) diblock copoly mer as emulsifier. In addition to its emulsifying effect, it was shown that a block copolymer containing a crystalline PEO sequence has a te ndency to form micelles as well as supramolecular structures in nonpol ar solvent such as methylcyclohexane. The filmification of the emulsio n by solvent evaporation and the film morphology were examined by ligh t and electron microscopy and by nuclear magnetic resonance (NMR) T-2 and self-diffusion measurements. Microscopic evaluations have shown ca vities having an average size, depending on the copolymer content, of a few micrometers and filled with liquid PEG. Additionally, smaller st ructures typically in the range of 30-50 nm have been observed by tran smission electron microscopy and are attributed to crystalline lamella e formed by the copolymer in the matrix. The T-2 measurements reveal t hree contributions to the transverse magnetization decay: one of the S EBS matrix, one of the liquid within the cavities and one of the liqui d dissolved in the smaller structures formed by the copolymer in the m atrix. In the pulsed field gradient NMR self-diffusion experiments two self-diffusion coefficients were found, one of the liquid in the cavi ties and one of the liquid dissolved in the matrix within the smaller structures. Generally, a restricted diffusion is observed in that latt er case owing to confining structures of the diffusing liquid molecule s. (C) 1998 John Wiley & Sons, Ltd.