Structural changes and crystallization kinetics of polylactide under CO₂investigated using high-pressure Fourier transform infrared spectroscopy

Abstract

The structural changes and crystallization kinetics of polylactide (PLA) during cold crystallization under CO 2 at 80 ∘ C were studied using in situ high-pressure Fourier transform infrared (FTIR) spectroscopy. The FTIR spectra show that PLA can crystallize under air and CO 2 , and some differences are observed. In the second-derivative spectra, the 1220 cm −1 band is only found for PLA crystallized under CO 2 , and the tt conformer of PLA crystallized under CO 2 is located at 1749 cm −1 , while that of PLA crystallized under air is located at 1751 cm −1 . From wide-angle X-ray diffraction, only the ′ -crystal is observed when PLA is crystallized under air, whereas the -crystal appears when crystallized under CO 2 . The crystalline-sensitive bands at 921 and 1458 cm −1 were used to analyze the crystallization kinetics of PLA. When PLA crystallizes under air, the 1458 cm −1 band changes faster than the 921 cm −1 one; when it crystallizes under CO 2 , the result reverses. This suggests that CO 2 hinders interchain interactions while promoting the helix conformation.

Comparative Study of Crystallization, Mechanical Properties, and In Vitro Cytotoxicity of Nanocomposites at Low Filler Loadings of Hydroxyapatite for Bone-Tissue Engineering Based on Poly(l-lactic acid)/Cyclo Olefin Copolymer

“…The synthesized nHA compound was subjected to FTIR as shown in Figure 3a. The presence of peaks at 1092 (PO 4 3− , ν 1 ), 1023 (PO 4 3− , ν 1 ), 963 (OH −1 ), 601 (HPO 4 2− ), and 561 cm −1 (PO 4 3− , ν 3 ) were the characteristic bands for nHA confirming its successful synthesis [35,36]. A very small peak of OH was visible at 3571 cm −1 affirming that the amount of H 2 O was very low.…”

The improved foaming behavior of PLA caused by the enhanced rheology properties and crystallization behavior via synergistic effect of carbon nanotubes and graphene

“…[2][3][4][5] PLA foams prepared via scCO 2 technology have been investigated widely thanks to its nature: renewable resources, biocompatibility, and biodegradability. 6,7 Nevertheless, the poor melt strength of PLA leads to the coalescence and collapse of cells during the foaming process, which impairs properties of products such as mechanical property and expansion ratio. Therefore, it is vital to enhance the melt strength of PLA.…”

“…To prepare microcellular foams, supercritical carbon dioxide (scCO 2 ) is usually used as blowing agent due to its environmental friendly nature 2–5 . PLA foams prepared via scCO 2 technology have been investigated widely thanks to its nature: renewable resources, biocompatibility, and biodegradability 6,7 . Nevertheless, the poor melt strength of PLA leads to the coalescence and collapse of cells during the foaming process, which impairs properties of products such as mechanical property and expansion ratio.…”

Foaming behavior of poly(lactic acid) with different D-isomer content based on supercritical CO2-induced crystallization

“…26 , 27 The effects of compressed CO 2 on the crystallization behavior of PLA have been extensively studied, and various kinds of crystalline morphologies depending on the D/L ratios and CO 2 -treatment conditions were obtained. 28 , 29 In particular, the ring-banded spherulites were formed from the glassy PLA with low L-isomer content via cold-crystallization in compressed CO 2 . 30 Therefore, the D/L ratio is another important parameter that can affect the PLA’s crystallization and melting behaviors.…”