Morphology study of poly(gamma-benzyl L-glutamate) (PBLG) and polyisoprene (PI) block copolymer using pulsed NMR and electron microscope revealed that the solid block copolymer is in microphase separated state. NMR measurement detected the interface of the block copolymer. Spin-lattice relaxation time T-1 of the block copolymer gave the domain size which is in good agreement with the result obtained from the electron microscopy. (C) 1997 Elsevier Science Ltd.