Enhanced Crystallization Rate of Poly(l-lactide) Mediated by a Hydrazide Compound: Nucleating Mechanism Study

A low molecular weight hydrazide compound, tetramethylenedicarboxylic di (2-hydroxybenzohydrazide) (TMBH), greatly improves the crystallization rate and crystallinity of poly(l-lactide) (PLLA). The nucleating efficiency of TMBH on the crystallization of PLLA exhibits obvious concentration dependence, which increases first and then decreases slightly with the increase of TMBH loading, reaching a maximum at 0.3 wt%. Time-resolved Fourier transform infrared spectroscopy spectra indicate that the formation of skeletal conformational ordering structure of PLLA has been accelerated in the presence of TMBH, which can act as efficient precursors speeding up both the nucleation of PLLA on TMBH surface and the formation of intrachain 10(3) helix structure. The possible hydrogen bonding interaction between the OH or NH groups in TMBH and the CO groups in PLLA backbones is supposed to be an important factor, which promotes the migration of PLLA chains to TMBH crystallites and the emergence of interchain interactions as well as the conformational ordering.