Synthesis and stereocomplex formation of enantiomeric alternating copolymers with two types of chiral centers, poly(lactic acid--2-hydroxybutanoic acid)s

• Published in: RSC advances 2020-10, Vol.1 (64), p.39-397
• Main Authors: Tsuji, Hideto, Nakayama, Kazuya, Arakawa, Yuki
• Format: Article
• Language: English
• Subjects: Acids; Biodegradability; Biodegradable materials; Chemical synthesis; Chemistry; Copolymers; Crystal structure; Crystallinity; Crystallization; Enthalpy; Melt temperature; Mixtures; NMR; Nuclear magnetic resonance; Physical properties; Polylactic acid; Spectra; Spectrum analysis; Thermodynamic properties
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/d0ra08351h

Stereocomplex (SC) formation was reported for the first time for enantiomeric alternating copolymers consisting of repeating units with two types of chiral centers, poly(lactic acid- alt -2-hydroxybutanoic acid)s [P(LA- alt -2HB)s]. l , l -Configured poly( l -lactic acid- alt - l -2-hydroxybutanoic acid) [P(LLA- alt - l -2HB)] and d , d -configured poly( d -lactic acid- alt - d -2-hydroxybutanoic acid) [P(DLA- alt - d -2HB)] were amorphous. Blends of P(LLA- alt - l -2HB) and P(DLA- alt - d -2HB) were crystallizable and showed typical SC-type wide-angle X-ray diffraction profiles similar to those reported for stereocomplexed blends of poly( l -lactic acid) and poly( d -lactic acid) homopolymers and of poly( l -2-hydroxybutanoic acid) and poly( d -2-hydroxybutanoic acid) homopolymers, and of l , l -configured poly( l -lactic acid- co - l -2-hydroxybutanoic acid) [P(LLA- co - l -2HB)] and d , d -configured poly( d -lactic acid- co - d -2-hydroxybutanoic acid) [P(DLA- co - d -2HB)] random copolymers. The melting temperature values and melting enthalpy values at 100% crystallinity for stereocomplexed solvent-evaporated and precipitated P(LLA- alt - l -2HB)/P(DLA- alt - d -2HB) blends were correspondingly 187.5 and 187.9 °C, and 98.1 and 91.8 J g −1 . Enantiomeric polymer blending of P(LLA- alt - l -2HB) and P(DLA- alt - d -2HB) can confer crystallizability by stereocomplexation and the biodegradable materials with a wide variety of physical properties and biodegradability are highly expected to be prepared by synthesis of alternating copolymers of various combinations of two types of chiral α-substituted 2-hydroxyalkanoic acid monomers and their SC crystallization. Stereocomplex formation was reported for alternating copolymers of chiral α-substituted 2-hydroxyalkanoic acids which can be utilized for preparation of biodegradable materials with a variety of physical properties and biodegradability.