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Stereocomplex crystallites can be formed only by the interaction of enantiomeric PLA chains (PLLA and PDLA), which can be controlled during melt processing. Further, sc‐PLA has a limited ability to reform its crystallinity after being melted (removal of thermal history). To improve the molecular interaction between PLLA and PDLA, Purnama et al. have studied stereocomplexation in the blend of PLLA and random copolymer (PDLCL) of D‐lactide with small amount of caprolactone (CL) [66]. The small amount of CL units in PDLCL act as soft fraction (due to the presence of methylene linkage) in the polymeric system to provide relatively low glass transition and melting temperatures. Further, this soft fraction accelerates the PDLA chain movement to easily interact with PLLA chains, thereby resulting in improved melt stability of sc crystallites. They also reported that the system resulted in the maximum sc crystallinity when the amount of CL was 2.5 unit‐mol%. It was however indicated that the excess use of CL may lead to overactive mobility of PDLA chains, ultimately affecting the stereocomplexation. In an another approach, Jikei et al. attempted to develop a segmented, random multiblock copolymer of PLLA and PCL and blended it with PDLA to improve the stereocomplexation [67]. The soft segment PCL aided in improving the elongation at break (over 400%) of PLLA, whereas preferential formation of stereocomplex crystallites in hard domain (containing PLLA and PDLA) contributed to enhancing the Young’s modulus (over 400 MPa) and ultimately improved the overall toughness of the blend. In particular, the physical crosslinking in hard domain also contributed to enhance the thermal deformation stability of the blend.

TABLE 5.2 Mechanical and Thermal Properties of the Representative Bio‐Based/Bio‐Degradable Polymers

	PLLA	sc‐PLA	PGA	PHB	PCL
T m (°C)	170–190	220–240	225–230	188–197	55–65
T g (°C)	50–65	65–72	40	5	−60
ΔH m (J/g)	93–203	142–155	180–207	146	136
Density (g/cm3)	1.25–1.3	1.21–1.342	1.50–1.69	1.18–1.26	1.1–1.15
Tensile strength (MPa)	120–2260	880	80–980	180–200	8–16
Young’s modulus (GPa)	6.9–9.8	8.6	3.9–1.4	4.9–5.9	0.1–0.4
Elongation at break (%)	12–16	30	30–40	50–70	100–2000

Furthermore, stereocomplexation involving alternating copolymers comprising lactic acid (LA) units have been studied extensively. For example, blending of enantiomeric alternating copolymer of LA and glycolic acid (GA) having molecular weight of 5000 Da leads to preferential formation of stereocomplex crystallites as reported by Tsuji et al. [68]. They proposed that blending of alternating LA‐based copolymers could be a versatile technique for the development of high‐performance bio‐based biodegradable materials with tunable physical properties and biodegradability. Yet another study reports the incorporation of alanine unit into LA units in random copoly(ester‐amides) with ester and amide linkages leading to the preferential formation of sc crystallites [69]. However, the developed polymers contain low degree of polymerization, and to have them employed in the commercial scale utility, further development is needed.