Polylactide cocrystals and gels

Abstract

Synthetic biodegradable polyesters have emerged as an alternative to conventional petroleum-derived polymers for a diverse range of applications. Among these, polylactides are the most commercially successful biodegradable polymers. The presence of stereoregular chains makes poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) semicrystalline. The blending of enantiomeric PLLA and PDLA resulted in the stereocomplex formation due to non-covalent interactions of enantiomeric chains. PLLA exhibits different crystalline forms depending on the crystallization conditions with different chain conformations, as well as different chain packing structures. PLLA and its blend with PDLA are known to form cocrystals with certain solvents. This review focuses mainly on the recent progress in understanding the cocrystal formation, polymorphic phase transitions of these cocrystals, gelation mechanism and stereocomplex formation in blend gels of polylactides.

Hydrogel-Assisted Microfluidic Wet Spinning of Poly(Lactic Acid) Fibers from a Green and Pro-Crystallization Spinning Dope

“…It was reported that ε solvents could induce the formation of PLAsolvent complex cocrystals, which then act as physical crosslinks and trigger the PLA sol-gel transition [19,58]. The herein discovered fully reversible PLA/Cyrene TM sol-gel transition indicates that Cyrene TM could be a green ε solvent for PLA.…”

“…PLA-solvent crystal complex were only reported in a few petroleum-based ε solvents, i.e⋅THF, CPO, DOL, GBL and DMF. Among these ε solvents, only DMF can induce the formation of PLA/ solvent cocrystal and gel at room temperature, others require much lower temperatures [19]. This is the first report of bio-based green solvent (Cyrene TM ) for inducing PLA crystallization and "sol-gel" transition at room temperature.…”

“…S2-F). It was reported that in PLA/DMF system, only α-crystals exist at temperature above 50 • C [19].…”

“…Some PLA solvents are known as ε solvents, which can induce PLA solution crystallization (ε form PLA-solvent complex) and subsequent gelation. Such ε solvents include dimethylformamide (DMF), cyclopentanone (CPO), 1,3-dioxolane (DOL), γ-butyrolactone (GBL), and tetrahydrofuran (THF) [19]. However, non-ε solvents such as dichloromethane (DCM) [16], methylene chloroform [20], chloroform [21], dimethyl sulfoxide (DMSO) [22], N-methyl pyrrolidone (NMP) [22], and hexafluoroisopropanol (HFIP) [23] were mainly used for wet spinning of PLA fibers.…”

The influence of Scutellaria baicalensis extract obtained from traditional Chinese herbal medicine on the thermo‐oxidative degradation and stabilization of plasticized polylactic acid

“…2,3 PLA can be completely degraded into carbon dioxide and water to re-enter the ecological cycle by microorganisms in nature under certain conditions. Due to its good mechanical properties (high strength, high modulus), processability, high transparency, biocompatibility, and good biodegradability, PLA materials have attracted tremendous attention, [4][5][6][7][8][9][10][11] and exhibit a wide range of applications in agriculture, 12 packaging, [13][14][15] biomedicine, [16][17][18][19][20][21][22] textile, 23 transportation, 24 and electronics. 25 However, the brittleness of PLA restricts its processing ability.…”