Enhanced Crystallization Rate of Poly(L-lactide)/Hydroxyapatite-graft-poly(D-lactide) Composite with Different Processin
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ARTICLE
POLYMER SCIENCE
https://doi.org/10.1007/s10118-020-2374-1 Chinese J. Polym. Sci.
Enhanced Crystallization Rate of Poly(L-lactide)/Hydroxyapatite-graftpoly(D-lactide) Composite with Different Processing Temperatures Min Wang, Lei-Chu You, Yu-Qi Guo, Ni Jiang, Zhi-Hua Gan, and Zhen-Bo Ning* State Key Laboratory of Organic-Inorganic Composites, Beijing Laboratory of Biomedical Materials, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029, China
Electronic Supplementary Information Abstract Hydroxyapatite-graft-poly(D-lactide) (HA-g-PDLA) was synthesized by ring-opening polymerization with HA as initiator and stannous octanoate (Sn(Oct)2) as catalyst. Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) results indicate that PDLA chains are successfully grafted onto HA particles by covalent bond. Under two different processing temperatures (190 and 230 °C), the effect of the grafted PDLA chains on the crystallization behavior of poly(L-lactide)/HA-g-PDLA (PLLA/HA-g-PDLA) composite was investigated in the current study, comparing to neat PLLA and its four composites (PLLA/HA, PLLA/HA-g-PLLA, PLLA/PDLA, and PLLA/HA/PDLA). The crystallization rate of PLLA/HA-g-PDLA composite is highly enhanced comparing to PLLA, PLLA/HA and PLLA/HA-g-PLLA composites in which there are no stereocomplex (SC) crystallites. In addition, when the processing temperature rises from 190 °C to 230 °C, the acceleration of PLLA crystallization in PLLA/HA-g-PDLA composite is not influenced so much as other composites containing SC crystallites, such as PLLA/HA/PDLA or PLLA/PDLA. The differential scanning calorimetry (DSC) results demonstrate that even without SC crystallites, the crystallization of PLLA can still be accelerated a lot in this composite. This may be related to the interaction between the grafted PDLA chains and the amorphous PLLA chains in PLLA/HA-g-PDLA composite. The isothermal crystallization kinetics studies indicate that the nature of nucleation and crystal growth of PLLA/HAg-PDLA composite are more likely 3D crystalline growth with heterogeneous nucleation mode, which are different from PLLA or other composites. This investigation could shed new light on the application of PLLA/HA composites. Keywords HA particles; Stereocomplexation; Composite; Crystallization Citation: Wang, M.; You, L. C.; Guo, Y. Q.; Jiang, N.; Gan, Z. H.; Ning, Z. B. Enhanced crystallization rate of poly(L-lactide)/hydroxyapatite-graft-poly(Dlactide) composite with different processing temperatures. Chinese J. Polym. Sci. https://doi.org/10.1007/s10118-020-2374-1
INTRODUCTION Poly(lactide) (PLA) has been well investigated for its excellent properties, such as biodegradability, biocompatibility, and desired mechanical properties.[1−3] It has therefore been applied to the preparation of controlled release drugs, tissue engineering, and bone fracture fixation.[4−6] PLA possesses three stereochemical forms: poly(L-lactide) (PLLA), poly(D-lactide) (PDLA), and p
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