The confined crystallization behavior of the dendritic block copolymer poly(-caprolactone)-b-polystyrene (D-PCL-b-PS) was investigated under asymmetric chain ends restriction of PCL blocks. At the beginning

the block copolymer was synthesized through combination of ring opening polymerization (ROP) and atom transfer radical polymerization (ATRP). The crystallizability of PCL block varied significantly with this specific dendritic molecular structure. During the nonisothermal crystallization process

only a fraction of slightly restricted PCL blocks could form crystals through extinct cold crystallization

and the significantly restricted PCL blocks was unable to crystallize during the limited cold crystallization process. Further isothermal crystallization was carried out to make samples completely crystallize. It was found when the crystallization temperature was below 30℃

double melting peaks were observed on the DSC curves of the samples

with the lower peak at nearly 40℃ and the higher at 50℃. The two peaks shifted to higher temperature regions and got closer with increasing isothermal crystallization temperature. When the isothermal crystallization temperature reached 40℃

the two melting peaks were not distinct any more. The lower melting point was corresponding to the fusion of the unperfect crystals formed by significantly restricted PCL blocks

and the higher melting point was ascribed to the melting of the relatively well-developed crystals formed by slightly restricted PCL blocks. A model indicating the conformations of PCL blocks under different degrees of chain end restriction was suggested.