The crystallization behaviors of single 2-bromopropionyl end-capped poly(L-lactide) (PLLA-Br) were studied to investigate the end group effect during polymer crystallization.PLLA was first synthesized through ring opening polymerization (ROP) using benzyl alcohol as initiator.Then the free hydroxyl end group of PLLA was modified into big rigid 2-bromopropionyl group to obtain PLLA-Br.It was found that PLLA-Br with single 2-bromopropionyl end group possessed higher glass transition temperature than PLLA

indicating that the introduced 2-bromopropionyl end group restricted the chain mobility of PLLA.More interestingly

the 2-bromopropionyl end group greatly affected the crystallization process of PLLA.During non-isothermal crystallization process

the cold crystallization temperature of PLLA-Br was about 12℃ lower than that of PLLA; During isothermal crystallization process after quenching to room temperature

the number of simultaneously growing spherulites (per unit volume) was much higher in the PLLA-Br sample than in PLLA.These results could be attributed to the facilitated nucleation ability of PLLA-Br during cooling process after modification by 2-bromopropionyl end group.Moreover

during isothermal crystallization process directly from melt

both the temperature window for PLLA to form regular banded spherulites and maximum spherulite growing temperature shifted to higher temperature region after end capping

while crystalline structure was identical.This may provide a simple and effective method for PLLA modification to modulate its crystallizability.