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 2 H spin-lattice relaxation time, T 1 , of EP soft segments above their glass transition temperature was measured by solid-state 2 H NMR spectroscopy. It was found that the block copolymers had a fast and a slow T 1 component whereas EP copolymer had only a fast component. The fast T 1 components for SEP and SEPS are similar to the T 1 value of EP above ca 20• C. The slow T 1 component for SEP and SEPS exhibited a minimum at 60• C and approached the value of the fast component near the T g of polystyrene. The motional behavior of the EP units for SEP is similar to that of SEPS over the entire range of temperature.

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