Increased gt Conformer Contents of PLLA Molecular Chains Induced by Li-TFSI in Melt: Another Route to Promote PLLA Crystallization

Abstract

Much attention has been paid on promotion of Poly(L-lactic acid) (PLLA) crystallization. The incorporation of nucleation agents is a commonly used way to enhance the PLLA crystallization. In this work, we reported another efficient strategy to accelerate PLLA crystallization by the conformational pre-ordering of PLLA molecular chains in melt. The organic salt bis(trifluoromethysulfonyl)imide lithium salt (LiTFSI) was incorporated into PLLA and the effects of LiTFSI on the crystallization of PLLA were investigated. It was found that LiTFSI is thermodynamically miscible with PLLA and the anion of LiTFSI interacts with PLLA molecular chains strongly. Small amount of LiTFSI can accelerate the crystallization of PLLA drastically and 0.5 wt % addition gives the best nucleation effects for PLLA. The in situ Fourier transform infrared spectroscopy results revealed that the pre-ordering structure of PLLA chains was formed in the melt with the incorporation of LiTFSI. It was clearly demonstrated that the relative population of gt conformer (corresponding to 10 3 helical conformation of α-form PLLA crystal) in PLLA/LiTFSI composites was higher than that of neat PLLA because of the interactions between LiTFSI and PLLA. Therefore, a lower energy barrier for PLLA nucleation was achieved by trace of LiTFSI because of the enhanced gt conformer contents. This work offers an alternative strategy to enhance PLLA crystallization by small molecules induced conformational pre-ordering.

Arrested Elongated Interface with Small Curvature by the Simultaneous Reactive Compatibilization and Stereocomplexation

“…Figure e illustrates the enlarged FT-IR spectra of the i-SC-blend, collected upon cooling, within the fingerprint region (980–880 cm –1 ). The peak at 921 cm –1 , which was characteristic of the coupled C–C backbone stretching with methyl rocking mode, is assigned to the 10 3 helix chain conformation of PLLA. − Meanwhile, the band around 908 cm –1 corresponded to stereocomplexation (SC) of PLLA/PDLA (β-crystals) . The intensities of the characteristic peaks at 921 and 908 cm –1 from Figure e were directly calculated and are shown in Figure f.…”

PY13FSI-Infiltrated SBA-15 as Nonflammable and High Ion-Conductive Ionogel Electrolytes for Quasi-Solid-State Sodium-Ion Batteries

“…After being immobilized with Na-IL, the characteristic absorption peak of O–H migrates to a higher wavenumber of 3506 cm –1 and becomes sharper. Based on the hydrogen bond’s saturation and stronger electron-withdrawing ability of F than O, we speculate that more active Si–OH groups are generated instead of the hydrogen bond in bridged silanols, forming more stable hydrogen bonds with F (Figure e) . Moreover, the electron cloud on O–H...F is biased toward H due to the strong electron-withdrawing ability of F and O, which results in an increase in the force constant on the O–H bond and eventually leads to the blue shift of the OH bond vibration.…”

Ternary Poly(ethylene oxide)/Poly(l,l-lactide) PEO/PLA Blends as High-Temperature Solid Polymer Electrolytes for Lithium Batteries

“…Recently, Xie et al found that lithium bis­(trifluoromethanesulfonyl)­imide (LiTFSI) is thermodynamically miscible with PLA and that a small amount of LiTFSI can improve the crystallization ability of PLA. Also, the anion has a strong interaction with the PLA . In addition, the interaction between the carbonyl group of PLA with Li-ions from LiTFSI has also been reported …”

“…Also, the anion has a strong interaction with the PLA. 19 In addition, the interaction between the carbonyl group of PLA with Li-ions from LiTFSI has also been reported. 20 Given these unique characteristics of PLA, we decided to investigate PEO/PLA blends, as these polymers have partial or total miscibility in their amorphous regions depending on the composition and molecular weight of the homopolymers.…”