To investigate the influence of the branch structure of four-arm poly(L-lactide) (4A-PLLA) on the crystallization behavior of linear poly(L-lactide) (linear PLLA)

a series of non-isothermal programs were carried out on a differential scanning calorimeter (DSC) and a polarized light microscope (PLM) equipped with a hot stage.The samples were heated to 200℃/180℃/170℃/160℃ to obtain totally-melting and partially-melting status.According to PLM images after cooling to room temperature

it was proved that the branch structure of 4A-PLLA could promote the crystallization at a cooling rate of 10 K/min when the content of 4A-PLLA exceeded 3 wt% after totally-melting at 180℃ and higher.On the other hand

partially-melting 4A-PLLA and linear PLLA could both act as the nucleating agents in the aforementioned cooling program after melting at 170℃ and lower to promote the crystallization of the blends.Partially-melting samples displayed stronger crystallization and weaker cold crystallization in the cooling and the 2nd heating programs

while the PLM images illustrated more crystalline regions with smaller size for blends with higher 4A-PLLA contents after cooling to the room temperature.The second heating curves of samples showed higher high-melting temperatures as 4A-PLLA contents increased

which was attributed to the crystallization perfection effect of 4A-PLLA and its proportion rising in the crystals of the 4A-PLLA/linear PLLA blends.