The relationship between solubility and nucleating effect of organic nucleating agent in poly(L-lactic acid)

N,N′-bis(benzoyl) hexanedioic acid dihydrazide (BHAD), and N,N′-bis(benzoyl) terephthalic acid dihydrazide (BTAD) were synthesized as the organic nucleating agents for poly(L-lactic acid) (PLLA). These two organic compounds exhibited different nucleating effect to PLLA. When the concentration was very low, BTAD was able to nucleate PLLA, while BHAD was not. When the concentration was adequate, BHAD showed better nucleating effect than BTAD. The experiments showed that, BHAD had the ability of dissolving into PLLA melt matrix, while BTAD was insoluble in PLLA. The optical microscope images revealed the quite different PLLA crystal morphologies nucleated by BHAD and BTAD. As BTAD could not dissolve in PLLA melt, it only induced a mass of small grain crystals of PLLA, the morphology of which is the same as neat PLLA. BHAD had relatively different nucleation and crystallization behaviors. Upon heating, BHAD could partially or totally dissolve in PLLA melt, which depended on the final heating temperature and its concentration. Upon cooling, BHAD separated from PLLA matrix and formed needle like or dendritic structures. Moreover, totally dissolved BHAD could finally exhibit dendritic structures, which had an excellent nucleation effect to PLLA. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46851.