Recent Progress in Enhancing Poly(Lactic Acid) Stereocomplex Formation for Material Property Improvement

Abstract

The production and utilization of polymers have been widely implemented into diverse applications that benefit modern human society, but one of the most valuable properties of polymers, durability, has posed a long-standing environmental challenge from its inception since plastic waste can lead to significant contamination and remains in landfills and oceans for at least hundreds of years. Poly(lactic acid) (PLA) derived from renewable resources provides a sustainable alternative to traditional polymers due to its advantages of comparable mechanical properties with common plastics and biodegradability. However, the poor thermal and hydrolytic stability of PLA-based materials limit their potential for durable applications. Stereocomplex crystallization of enantiomeric poly (l-lactide) (PLLA) and poly (d-lactide) (PDLA) provides a robust approach to significantly enhance material properties such as stability and biocompatibility through strong intermolecular interactions between L-lactyl and D-lactyl units, which has been the key strategy to further PLA applications. This review focuses on discussing recent progress in the development of processing strategies for enhancing the formation of stereocomplexes within PLA materials, including thermal processing, additive manufacturing, and solution casting. The mechanism for enhancing SC formation and resulting material property improvement enabled by each method are also discussed. Finally, we also provide the perspectives on current challenges and opportunities for improving the understanding of processing-structure-property relationship in PLA materials that could be beneficial to their wide practical applications for a sustainable society.

Stereocomplex Polylactide for Drug Delivery and Biomedical Applications: A Review

“…Recently, numerous studies have reported that stereocomplex polylactide (sc-PLA) with improved physical characteristics can be used in drug delivery and as molecular carriers [ 10 , 11 , 12 ]. Nanoparticles, such as microspheres and micelles of sc-PLA, have the advantage of controlling drug uptake and release patterns through their synthesis and modification, as well as natural adsorption.…”

Properties Enhancement of High Molecular Weight Polylactide Using Stereocomplex Polylactide as a Nucleating Agent

“…As the crystal structure of s-PLA has unique characteristics with higher thermal and mechanical properties, crystalline s-PLA can be utilized as a nucleating agent to improve the thermal and mechanical properties of PLA [8,11]. Many studies have reported strategies to improve the properties of PLA through s-PLA formation [12][13][14][15][16][17].…”

“…The presence of s-PLA crystalline with various chain structures in the PLA brings higher mechanical and thermal properties [16]. Property enhancement by s-PLA will affect PLA processing: thermal processing, additive manufacturing, and solution casting [17]. Thermal and mechanical enhancement of PLA through stereocomplexation has been utilized to obtain stable PLA materials which are suitable for many applications, especially use as high-performance materials [8,[14][15][16][17][18][19][20][21].…”

“…Property enhancement by s-PLA will affect PLA processing: thermal processing, additive manufacturing, and solution casting [17]. Thermal and mechanical enhancement of PLA through stereocomplexation has been utilized to obtain stable PLA materials which are suitable for many applications, especially use as high-performance materials [8,[14][15][16][17][18][19][20][21]. The mechanical and thermal properties of s-PLA are higher than those of pure PLA films, which is caused by the strong molecular interactions (hydrogen bonds and dipole-dipole interactions) of PLLA and PDLA chains [21][22][23][24].…”

Extruded PLA Nanocomposites Modified by Graphene Oxide and Ionic Liquid

“…In general, the mechanical properties of PLA are similar to those of common fossil fuel-based thermoplastics; however, the glass transition temperature (T g ), ductility, and thermal stability are lower. Thus, different types of additives are commonly used to improve the properties of PLA [ 13 , 14 , 15 , 16 ].…”