has been achieved during electrospinning along with its functionalization, where the sub‐micrometer dispersion of nanofillers, namely polyhedral oligomeric silsesquioxanes (POSS), has been established. The functionalized sc‐PLA retains the capability of forming pure stereocomplex upon annealing [91]. Nevertheless, efforts have also been made to tune the hydrolytic degradation of sc‐PLA by tailoring the backbone architecture. Stereocomplexation between PLLA and PDLA oligomers has been reported, where the polymer architecture and the end groups altered the hydrolytic degradation rate [92]. Namely, the linear sc architecture having alcoholic end groups exhibited an increased degree of stereocomplexation with higher hydrolytic stability. In contrast, for the polymer with carboxyl chain ends, the degradation was accelerated due to the lower degree of stereocomplexation. The use of sc‐PLA has also been explored in textiles and membranes for oil–water separation. The modification of PLA nonwoven fabric by the formation of sc crystals has been reported by Zhu et al., where the sc crystal phase increased the surface roughness, as well as imparted oleophilicity to the fabric. The modification of the surface by sc‐PLA increased the oil absorption capability by 30–40% [93], which can be repeatedly used for the same purpose. The sc‐PLA, being brittle in nature, is limited to only specific applications. When exploring sc‐PLA for tissue engineering applications, elasticity is often required for the scaffold materials to serve physiological functions [94, 95]. This may be made possible by using toughness modifiers [96, 97]. For example, poly(butylene adipate‐co‐terephthalate) (PBAT) may be regarded as a toughness modifier when loaded into the matrix of PLA to increase elongation and processability [98]. The sc‐PLA/PBAT scaffolds with high porosity have been prepared by Kang et al. by non‐solvent phase separation [99]. The sc‐PLA‐based scaffolds led to a uniform porous structure (as compared to PLLA‐ or PDLA‐based scaffolds) having a wall thickness of ~1 μm, which may be due to the intermolecular forces between the enantiomeric PLA chains. The sc‐PLA/PBAT scaffolds are capable of supporting the adhesion of fibroblast cells, which in turn accounts for its biocompatible nature.
5.8 CONCLUSIONS
Stereocomplexation in PLA has resulted in widespread acceptance accounting to its unique thermal, mechanical, and physical properties. The current chapter has underlined various techniques of achieving improved stereocomplexation in PLA, such as stereoblock formation, copolymerization, and composite formation. These techniques result in the formation of intended materials with customized properties, which have been manifested in the current chapter. Further, insights have been made into the melt‐crystallizability of sc‐PLA in view of improving its industrial applications. An emphasis has also been laid on improving the biocompatibility of sc‐PLA‐based materials for potential biomedical applications. It may be recognized that the bio‐based polymers/copolymers/composites built on sc‐PLA could replace the conventional polymers in multifaceted applications and reduce the human dependence on fossil resources, as well as the carbon dioxide loading on the global sphere.
REFERENCES
1 1. M. Brzeziński, T. Biela, Stereocomplexed polylactides, in: S. Kobayashi, K. Müllen (Eds.), Encyclopedia of Polymeric Nanomaterials, Springer Berlin Heidelberg, Berlin, Heidelberg, 2014. p. 1–10.
2 2. Y. Ikada, K. Jamshidi, H. Tsuji, S. H. Hyon, Stereocomplex formation between enantiomeric poly(lactides), Macromolecules 1987, 20(4), 904–906.
3 3. J. R. Murdoch, G. L. Loomis, Polylactide compositions, US4719246A, 1988.
4 4. F. Luo, A. Fortenberry, J. Ren, Z. Qiang, Recent progress in enhancing poly(lactic acid) stereocomplex formation for material property improvement, Front. Chem. 2020, 8, 688.
5 5. D. Karst, Y. Yang, Molecular modeling study of the resistance of PLA to hydrolysis based on the blending of PLLA and PDLA, Polymer 2006, 47(13), 4845–4850.
6 6. H. Tsuji in vitro hydrolysis of blends from enantiomeric poly(lactide)s. Part 4: well‐homo‐crystallized blend and nonblended films, Biomaterials 2003, 24(4), 537–547.
7 7. M. Kakuta, M. Hirata, Y. Kimura, Stereoblock polylactides as high‐performance bio‐based polymers, Polym. Rev. 2009, 49(2), 107–140.
8 8. H. Tsuji, Poly(lactic acid) stereocomplexes: a decade of progress, Adv. Drug Deliv. Rev. 2016, 107, 97–135.
9 9. M. Saravanan, A. J. Domb, A contemporary review on—polymer stereocomplexes and its biomedical application, Eur. J. Nanomed. 2013, 5(2), 81–96.
10 10. P. Pan, Y. Inoue, Polymorphism and isomorphism in biodegradable polyesters, Progr. Polym. Sci. 2009, 34(7), 605–640.
11 11. L. Han, P. Pan, G. Shan, Y. Bao, Stereocomplex crystallization of high‐molecular‐weight poly(l‐lactic acid)/poly(d‐lactic acid) racemic blends promoted by a selective nucleator, Polymer 2015, 63, 144–153.
12 12. S. Nagarajan, D. Krishnan, V. P. Sivaprasad, E. Bhoje Gowd, Chapter 5—Crystallization behavior of crystalline–amorphous and crystalline–crystalline block copolymers containing poly(l‐lactide), in: S. Thomas, P. M. Arif, E. B. Gowd, N. Kalarikkal (Eds.), Crystallization in Multiphase Polymer Systems, Elsevier, Amsterdam, 2018, pp. 93–122.
13 13. H. Tsuji, F. Horii, S. H. Hyon, Y. Ikada, Stereocomplex formation between enantiomeric poly(lactic acid)s. 2. Stereocomplex formation in concentrated solutions, Macromolecules 1991, 24(10), 2719–2724.
14 14. K. Scheuer, D. Bandelli, C. Helbing, C. Weber, J. Alex, J. B. Max, et al., Self‐assembly of copolyesters into stereocomplex crystallites tunes the properties of polyester nanoparticles, Macromolecules 2020, 53(19), 8340–8351.
15 15. B. Na, J. Zhu, R. Lv, Y. Ju, R. Tian, B. Chen, Stereocomplex formation in enantiomeric polylactides by melting recrystallization of homocrystals: crystallization kinetics and crystal morphology, Macromolecules 2014, 47(1), 347–352.
16 16. H. Tsuji, S. Yamamoto, Enhanced stereocomplex crystallization of biodegradable enantiomeric poly(lactic acid)s by repeated casting, Macromol. Mater. Eng. 2011, 296(7), 583–589.
17 17. R. Lv, N. Peng, T. Jin, B. Na, J. Wang, H. Liu, Stereocomplex mesophase and its phase transition in enantiomeric polylactides, Polymer 2017, 116, 324–330.
18 18. E. M. Woo, L. Chang, Crystallization and morphology of stereocomplexes in nonequimolar mixtures of poly(l‐lactic acid) with excess poly(d‐lactic acid), Polymer 2011, 52(26), 6080–6089.
19 19. L. Gardella, A. Basso, M. Prato, O. Monticelli, On stereocomplexed polylactide materials as support for PAMAM dendrimers: synthesis and properties, RSC Adv. 2015, 5(58), 46774–46784.
20 20. A. Gupta, N. Mulchandani, M. Shah, S. Kumar, V. Katiyar, Functionalized chitosan mediated stereocomplexation of poly(lactic acid): influence on crystallization, oxygen permeability, wettability and biocompatibility behavior, Polymer 2018, 142, 196–208.
21 21. L. Bouapao, H. Tsuji, Stereocomplex crystallization and spherulite growth of low molecular weight poly(l‐lactide) and poly(d‐lactide) from the melt, Macromol. Chem. Phys. 2009, 210(12), 993–1002.
22 22. T. Biela, A. Duda, S. Penczek, Enhanced melt stability of star‐shaped stereocomplexes as compared with linear stereocomplexes, Macromolecules 2006, 39(11), 3710–3713.
23 23. L. Jiang, P. Lv, P. Ma, H. Bai, W. Dong, M. Chen, Stereocomplexation kinetics of enantiomeric poly(l‐lactide)/poly(d‐lactide) blends seeded by nanocrystalline cellulose, RSC Adv. 2015, 5(87), 71115–71119.
24 24. Z. Xiong, X. Zhang, R. Wang, S. de Vos, R. Wang, C. A. P. Joziasse, et al., Favorable formation of stereocomplex crystals in poly(l‐lactide)/poly(d‐lactide) blends by selective
