Cis-1

4-polybutadiene synthesized by lanthanide catalyst (Ln-PB) was fractionated by precipitation method (toluene/methanol) into 5 fractions. Crystallization of each fraction was carried out at -30℃ and its morphological structure was investigated by transmisson electron microscopy. The structure parameters of entanglement network were obtanied from experimental relaxation spectrum. It has been found that the morphology and rate of crystallization depend not only on the stereoregularity

but also on the molecular weight and molecular weight fraction crystallized primarily with predetermined nuclei

and its lamellae are not entangled

while the high molecular weight fraction crystallized primarily from sporadic nuclei

and accompanied by lamellae entanglement. The nu-claetion and growth of crystallization depend on the average molecular weight of entang-lement segment Me.