Abstract
Poly(D-lactic acid) (PDLA) with different polyethylene glycol (PEG) segment synthesized PDLA-PEG-PDLA triblock copolymer through the ring-opening reaction of D-LA and PEG will be used as a toughening modifier. The microstructure, crystal structures and crystallization behaviors of this triblock copolymer were investigated by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The triblock copolymer is synthesized from the appearance of CH2 stretching vibration peak at 2910 cm−1 and C-O stretching vibration peak at 1200 cm−1 from PEG in FTIR spectra. Moreover, the chemical shift that is about 3.6 ppm in 1H NMR and 68.8ppm in 13C NMR proves this matter. The results of XRD and DSC reveal that PDLA and PEG are crystallized separately, and are not fully compatible, and microphase separation has occurred in this triblock copolymer. PEG can induce the triblock copolymer to accelerate the rate of crystallization, allowing it to crystallize more completely in the same amount of time. When the molecular weight of PEG is 6000 or the ratio of D-LA/PEG is 1/1, the crystallizability of PDLA-PEG-PDLA triblock copolymer is the best.
Highlights
Poly(D-lactic acid) (PDLA) with different polyethylene glycol (PEG) segment synthesized PDLAPEG-PDLA triblock copolymer through the ring-opening reaction of D-LA and PEG will be used as a toughening modifier
The effect of different PEG molecular weight and the ratio of D-LA/PEG on the microstructure, crystal structure and crystallization behaviors of copolymer was studied by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance spectroscopy (NMR), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and polarized optical microscopy (POM)
In the fingerprint region, there is a 1460 cm−1 bending vibration peak of CH2 and in the range of 1350 to 1310 cm−1 of chemical shift of methine (CH) bending vibration peaks. These absorption peaks prove the introduction of PEG structure in PDLA, and the presence of methyl and hypomethyl groups from PDLA and methylene groups from PEG in molecular chains, indicating that PDLA successfully copolymerized with PEG
Summary
Poly(D-lactic acid) (PDLA) with different polyethylene glycol (PEG) segment synthesized PDLAPEG-PDLA triblock copolymer through the ring-opening reaction of D-LA and PEG will be used as a toughening modifier. The effect of different PEG molecular weight and the ratio of D-LA/PEG on the microstructure, crystal structure and crystallization behaviors of copolymer was studied by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance spectroscopy (NMR), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and polarized optical microscopy (POM).
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