PLA stereo-complex

Polymer stereo-complexation results from stereoselective interactions between two complementing stereo-regular polymers which interlock to form a new material with altered physical properties in comparison with the parent polymers. The interactions are mainly stereoselective van der Waals forces. Stereo-complexation between PLLA and PDLA was first reported by Ikada et al. in 1987, and is now a well-known phenomenon for optically active PLA stereo-copolymers. In the past decades, the properties and potential applications of PLA stereo-complex have been extensively investigated. ... 

PLA homo-stereo-complexation can take plaee both in enantiomerie mixture and in stereo-bloeks of PLA-based polymers. The key parameter affecting stereo-complexation is the mixing ratio of PLLA to PDLA sequenees, the equimolar mixture yielding the optimal degree of stereo-eomplexation. PLA stereo-complex is usually prepared from eo-preeipitation of PLLA and PDLA in solution or through eooling from a melted mixture of both poly-mers. " Hetero-stereo-eomplexation between PLA and other optically active materials was also reported. ... 

In this contribution we intend to provide a eomprehensive review on PLA stereo-complex, including preparation, strueture-properties and biomedical applications. The effect of stereo-complex on the thermal dynamics, hydrolytic degradation, micellization and hydrogelation will be discussed. 

PLA stereo-complexes are obtained by co-crystallization of PLLA and PDLA in bulk or in organic solvents such as chloroform or acetonitrile. It has been shown that the minimal degree of polymerization (DP) of PLLA or PDLA oligomers for crystallization is 11, with corresponding melting temperature (Tm) at 59 °C and melting enthalpy (AH i) of 39 J g. In contrast, in blends of PLLA and PDLA oligomers, crystallization or stereo-complexation is... 

Interestingly, PLA stereo-complex can also be obtained during in vitro degradation of poly(DL-lactide), which is an intrinsically amorphous polymer. In fact, poly(DL-lactide) contains isotactic l-LA and d-LA se-... 

PLLA/PDLA Stereo-complex allows enhancing the thermal-resistance and mechanical properties as well as the hydrolytic stability of PLA-based materials. In the past decades, a great deal of work has been performed to exploit potential biomedical applications of PLA stereo-complex as shown in Table 2.1. ... 

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