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2H NMR spin relaxation study of the soft segment motion in alternating ethylene–propylene copolymers
Abstract:We synthesized three partially deuterated polymer samples, namely a poly(ethylene‐alt‐propylene) (EP) alternating copolymer, a poly(styrene‐b‐EP) diblock copolymer (SEP) and a poly(styrene‐b‐EP‐b‐styrene) triblock copolymer (SEPS). The 2H spin–lattice relaxation time, T1, of EP soft segments above their glass transition temperature was measured by solid‐state 2H NMR spectroscopy. It was found that the block copolymers had a fast and a slow T1 component whereas EP copolymer had only a fast component. The fast T1 components for SEP and SEPS are similar to the T1 value of EP above ca 20°C. The slow T1 component for SEP and SEPS exhibited a minimum at 60°C and approached the value of the fast component near the Tg of polystyrene. The motional behavior of the EP units for SEP is similar to that of SEPS over the entire range of temperature. Copyright © 2001 John Wiley & Sons, Ltd.
Keywords:NMR  solid‐state 2H NMR  block copolymer  spin–  lattice relaxation time
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