A Faster Approach to Stereocomplex Formation of High Molecular Weight Polylactide Using Supercritical Dimethyl Ether

Abstract

Engineering the polylactide via stereocomplexation with supercritical fluid (SCF) technology paved way to fabricate polymers with enhanced thermal and mechanical properties. We aimed to establish a SCF medium with excellent solubility for PLA without any additional solvent/co-solvent. We, therefore, employed supercritical dimethyl ether to synthesize 100% stereocomplex polylactide from high molecular weight homopolymers with an excellent yield. The remarkable solubility of the homopolymers in dimethyl ether is the key for quick conversion to s-PLA. This study proves a rapid synthesis route of dry s-PLA powder with sc-DME at 250 bar, 70 o C and 1.5 h, which are reasonably achievable processing parameters compared to the conventional methods. The degree of stereocomplexation was evaluated under the effect of pressures, temperatures, times, homopolymer-concentrations and molecular weights. An increment in the degree of stereocomplexation was observed with increased temperature and pressure. Complete conversion to s-PLA was obtained for PLLA and PDLA with M n~2 00 kg·mol -1 with a total homopolymer to total DME ratio of 6:100% w/w at prescribed reaction conditions. The degree of stereocomplexation was determined by DSC and confirmed by XRD. Considerable improvement in thermo-mechanical properties of s-PLA was observed. DSC and TGA analyses proved a 50 o C enhancement in melting transition and a high onset temperature for thermal degradation of s-PLA respectively.

Process intensification for the synthesis of ultra-small organic nanoparticles with supercritical CO2 in a microfluidic system

“…In this context, supercritical carbon dioxide (sc-CO2) offers distinct advantages for sustainable processes, as it is non-flammable, non-toxic and environmentally friendly. Amongst the myriad of sc-CO2-based processes, the supercritical antisolvent (SAS) process has been of particular interest for preparing micrometer- [10] and submicrometer-sized [11] particles from various organic materials, such as active pharmaceutical ingredients (APIs) [12] and polymers [13]. The particle morphology and size are affected by experimental parameters like temperature, pressure, molar ratio composition, solution concentration and flow rates, which highlights the importance of the thermo-hydrodynamic phenomena.…”

Strategy for Stereocomplexation of Polylactide Using O/W Emulsion Blending and Applications as Composite Fillers, Drug Carriers, and Self-Nucleating Agents

“…Polylactide (PLA), which is regarded as a promising biodegradable polymer, naturally exists in distinct forms of poly­( l -lactide) (PLLA) (levorotatory) and poly­( d -lactide) (PDLA) (dextrorotatory) owing to its chirality. − Formation of stereocomplex crystals can be induced between two enantiomers in racemic blends. , Stereocomplex PLA (sc-PLA) can possess significantly improved physical and mechanical properties as well as thermal resistance. Eco-friendly polymeric materials based on sc-PLA can be applied to applications that must endure high external stress and loads. , Stereocomplexation of PLA is commonly induced by solution blending, , melt blending, , and supercritical fluid (SCF) technology. , Our research group has been continuously investigating stereocomplexation for many years. − However, the methods developed thus far have many drawbacks, such as low processability, low yield, low solubility with solvent and solute, high cost, and slow production. It has been reported that PLLA/PDLA mixtures in solution induce the formation of stereocomplexes with distinctive physical and chemical stability due to their van der Waals interactions. , However, these supramolecular interactions are weak with reversible noncovalent interaction between molecules and are insufficient to induce rapid formation of stereocomplex crystal.…”

Supercritical fluid technology parameters affecting size and behavior of stereocomplex polylactide particles and their composites

“…To overcome these limitations, supercritical fluid (SCF) technology has been studied as a promising method for stereocomplexation [15][16][17][18][19]; this method can form sc-PLA particles with high yield and speed. Our research group has also researched many studies for a fast and facile approach of SCF technology on various perspectives [15,16,18,20,21]. Furthermore, these sc-PLA particles can be used as filler to make composites with a biodegradable PLLA matrix of the same composition [22][23][24][25].…”