Poly(lactide) Stereocomplexes: Formation, Structure, Properties, Degradation, and Applications

Abstract

Summary: Poly(lactide)s [i.e. poly(lactic acid) (PLA)] and lactide copolymers are biodegradable, compostable, producible from renewable resources, and nontoxic to the human body and the environment. They have been used as biomedical materials for tissue regeneration, matrices for drug delivery systems, and alternatives for commercial polymeric materials to reduce the impact on the environment. Since stereocomplexation or stereocomplex formation between enantiomeric PLA, poly(L‐lactide) [i.e. poly(L‐lactic acid) (PLLA)] and poly(D‐lactide) [i.e. poly(D‐lactic acid) (PDLA)] was reported in 1987, numerous studies have been carried out with respect to the formation, structure, properties, degradation, and applications of the PLA stereocomplexes. Stereocomplexation enhances the mechanical properties, the thermal‐resistance, and the hydrolysis‐resistance of PLA‐based materials. These improvements arise from a peculiarly strong interaction between L‐lactyl unit sequences and D‐lactyl unit sequences, and stereocomplexation opens a new way for the preparation of biomaterials such as hydrogels and particles for drug delivery systems. It was revealed that the crucial parameters affecting stereocomplexation are the mixing ratio and the molecular weight of L‐lactyl and D‐lactyl unit sequences. On the other hand, PDLA was found to form a stereocomplex with L‐configured polypeptides in 2001. This kind of stereocomplexation is called “hetero‐stereocomplexation” and differentiated from “homo‐stereocomplexation” between L‐lactyl and D‐lactyl unit sequences. This paper reviews the methods for tracing PLA stereocomplexation, the methods for inducing PLA stereocompelxation, the parameters affecting PLA stereocomplexation, and the structure, properties, degradation, and applications of a variety of stereocomplexed PLA materials. magnified image

Aggregation of polylactide with carboxyl groups at one chain end in the presence of metal cations

“…In WAXS profile (solid line in Fig. 11) the peaks characteristic for PLA stereocomplex [11] can be identified at 2h equal to 12.0°, 20.9°and 24.1°. WAXS profile obtained for the aggregation product of only one PLA stereoisomer is also shown in Fig.…”

“…Polymerizations of L-or Dlactide lead to two enantiomeric forms of polymer, namely poly(L-lactide) or poly(D-lactide). It is known that poly(L-lactide) and poly(D-lactide) form stereocomplexes with physical properties different from those of individual stereoisomers [11]. Thus, aggregation of a mixture of enantiomeric polylactides containing ionic groups should involve, in addition to interaction of ionic groups observed earlier for polycaprolactone, also an interaction of two chains of opposite chirality.…”

Fully bio-based, highly toughened and heat-resistant poly(L-lactide) ternary blends via dynamic vulcanization with poly(D-lactide) and unsaturated bioelastomer

“…3. The PLLA/VUB binary blends show amorphous feature without characteristic sharp peak, while PLLA/VUB/PDLA ternary blends show three distinct characteristic peaks at 2θ values of 11.8°, 20.7°a nd 23.9°, corresponding to the (110), (300)/(030), and (220) planes of SC crystallites, respectively [54]. In addition, the peak intensity increases with PDLA content, which is attributed to the increase in the content of SC crystallites.…”

Crystallization and hydrolytic/thermal degradation of a novel stereocomplexationable blend of poly(L-2-hydroxybutyrate) and poly(D-2-hydroxybutyrate)

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Stereocomplexation between PLLA and its enantiomer poly(D-lactide) (that is, poly(D-lactic acid) or PDLA) can yield biodegradable materials having superior mechanical performance and resistance to hydrolytic and thermal degradation relative to pure PLLA and PDLA. [16][17][18][19][20] Poly(2-hydroxybutyrate) (that is, poly(2-hydroxybutanoic acid) or P(2HB)) is a biodegradable polymer with the structure of a poly(lactide) (that is, poly(lactic acid) or PLA) in which methyl groups are substituted with ethyl groups.…”