Nanostructures of Stereocomplex Polylactide in Poly(l-lactide) Doped with Poly(d-lactide)

A Versatile Disorder-to-Order Technology to Upgrade Polymers into High-Performance Bioinspired Materials

Biodegradable polymer as traditional material has been widely used in the medical and tissue engineering fields, but there is a great limitation as to its inferior mechanical performance for repairing load-bearing tissues. Thus, it is highly desirable to develop a novel technology to fabricate high-performance biodegradable polymers. Herein, inspired by the bone's superstructure, a versatile disorder-to-order technology (VDOT) is proposed to manufacture a high-strength and high-elastic modulus stereo-composite self-reinforced polymer fiber. The mean tensile strength (336.1 MPa) and elastic modulus (4.1 GPa) of the self-reinforced polylactic acid (PLA) fiber are 5.2 and 2.1 times their counterparts of the traditional PLA fiber prepared by the existing spinning method. Moreover, the polymer fibers have the best ability of strength retention during degradation. Interestingly, the fiber tensile strength is even higher than those of bone (200 MPa) and some medical metals (e.g., Al and Mg). Based on all-polymeric raw materials, the VDOT endows bioinspired polymers with improved strength, elastic modulus, and degradation-controlled mechanical maintenance, making it a versatile update technology for the massive industrial production of high-performance biomedical polymers.

Entirely environment-friendly polylactide composites with outstanding heat resistance and superior mechanical performance fabricated by spunbond technology: Exploring the role of nanofibrillated stereocomplex polylactide crystals

This study aims at investigating the manufacturing and characterization of all-polylactide composites prepared by melt spunbond spinning technology. To do so, a series of asymmetric stereocomplex polylactide (SC-PLA) blends (PLLA 95 wt%/PDLA 5 wt%) was melt spun. To examine the impact of molecular structure of PDLA, the blends of linear PLLA, and low and high molecular weight as well as branched PDLAs, were subjected to a single step spunbond process. DSC thermograms of the samples showed two melting temperatures at around 170 °C and 210 °C, which were attributed to the melting of homo and stereocomplex crystals, respectively. The samples were spun at 190 °C, between the homo and stereocomplex crystals' melting temperatures, and at 230 °C, above the stereocomplex crystals' melting temperature. Morphology images showed the formation of fibers in the range of 40-50 μm. Shear rheological measurements revealed that the spun SC-PLA samples had a substantially higher viscosity and storage modulus in the low frequency region, and higher shear thinning behavior, compared to the non-spun samples. Extensional rheology measurements also showed that the spun samples demonstrated strain hardening behavior. Substantial enhancement of rheological properties was noted for the samples containing the branched and high molecular weight PDLA spun at 230 °C. After etching, the spun samples at 190 °C exhibited small spherical crystals with diameters in the range of 80-90 nm, whereas comparatively thin fibers in the size range of 60-70 nm were observed for the samples spun at 230 °C. Remarkable enhancements up to 100% and 60% was noted for the tensile modulus and strength, respectively, of the spun SC-PLA samples. The spun fibers also demonstrated a considerable reduction in boiling water and hot air shrinkage. The distinctive role of nanofibrillated stereocomplex crystals as a rheology modifier and a crystallization nucleating agent makes PLA more sustainable and paves the way for the fabricated all-PLA composites in applications requiring high heat resistance and superior mechanical performance. The present study unequivocally indicates a huge potential for the sustainable entirely all-PLA products manufactured by fiber in fiber and, indeed, unfolds unknown opportunities for PLA-based merchandises in future.

Poly(l-lactide) melt spun fiber-aligned scaffolds coated with collagen or chitosan for guiding the directional migration of osteoblasts in vitro

PLLA melt spun fiber-aligned scaffolds coated with collagen or chitosan enhance the viability, spreading, alignment and mobility of osteoblasts.

Stereocomplex poly(lactic acid) nanoparticles crystallized through nanoporous membranes and application as nucleating agent

Stereocomplex crystallization of poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) was performed by flowing their blended solution through nano-channels of porous membranes.