The morphology of the free surface of PEP copolymer samples was observed with TEM. It is shown that the morphology of the free surfaces of different samples varies one from another. Some consisted of "random lamellae"

while others consisted of both "random and regular lamellae". The structural nature of these two kinds of lamellae is discussed and is shown by other experimental evidence. The mechanical properties of the samples predicted on the basis of this consideration are in accordance with experimental results.