Unique Transitions in Morphology and Characteristics of Porous Poly(Lactic Acid) Enantiomers

Abstract

This study examines unique changes in the morphology and physical properties of monolithic poly(lactic acid) (PLA) enantiomers. It is revealed for the first time that PLA monoliths containing stereocomplex (sc) crystals are successfully produced using enantiomeric poly(L‐lactic acid) (PLLA) and poly(D‐lactic acid) (PDLA) using a simple phase separation process with ternary solvent (1,4‐dioxane/2‐butanone/water). The basic structure of the monoliths is changed drastically from needle‐like to spherical morphology until reaching a PLLA/PDLA ratio to equivalence. The PLA monolith prepared from a stoichiometric amount of PLLA/PDLA has high sc crystallinity without any homochiral crystals, and it shows higher melting temperature (226 °C), surface area (131 m2 g−1), and water contact angle (144.5°) compared with those of neat PLLA (180 °C, 86 m2 g−1, and 137.5°, respectively). Moreover, this sc‐PLA monolith exhibits excellent resistance to several good solvents of PLLA, whereas the pristine PLLA monolith is dissolved instantly in these solvents.

Tunable Wettability of Biodegradable Multilayer Sandwich-Structured Electrospun Nanofibrous Membranes

“…The fabrication of PLA and CA ENF membranes using the electrospinning technique is critical, and requires precise control over the processing parameters. A combination of polymer and solvent properties, including the polymer molecular weight, solution concentration, viscosity, surface tension, conductivity, vapor pressure, and solubility, have great influence on the development and morphology of ENFs [ 26 , 27 ]. During our preliminary tests, we have manipulated the electrospinning parameters to find a suitable solvent system and optimum processing conditions.…”

Spontaneous formation of hierarchical structures in some polylactide/polysilsesquioxane blends

“…The 3D interconnected macroporous structure of P/100-OH resembles that of PLA monoliths containing homocomplex (hc) and stereocomplex crystals obtained in a phase separation process with a ternary solvent mixture. 41 Interestingly, also in that case the structure generated by more needle-like hc-crystals was better defined than that formed by spherical sc-crystals. The effect was attributed to competitive gelation caused by liquid-liquid and solid-liquid phase separation with crystallization occurring in the polymer-rich domains within the liquid-liquid phase through spinodal decomposition (demixing between polymer rich and lean phase).…”

Critical parameters controlling the properties of monolithic poly(lactic acid) foams prepared by thermally induced phase separation

“…First, monoliths can be prepared from the corresponding monomers via polymerization induced phase separation, polymerization within high internal phase emulsion templates, and cryogelation . Second, monoliths can be produced via nonsolvent or thermally induced phase separation. In the former approach, monolith fabrication process from the corresponding monomers is complicated and homogeneous porous structures are difficult to obtain because polymerization and phase separation have to be controlled simultaneously.…”