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

Abstract

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.

Synthesis and Stereocomplexation of New Enantiomeric Stereo Periodical Copolymers Poly(l-lactic acid–l-lactic acid–d-lactic acid) and Poly(d-lactic acid–d-lactic acid–l-lactic acid)

“…72 As seen, P(LLA-LLA-DLA)/P(DLA-DLA-LLA) SC had a crystalline structure completely different from that of PLLA/PDLA SC, which has the typical SC diffraction profile. The typical SC diffraction profiles were observed for enantiomeric αsubstituted 2-hydroxyalkanoic acid-based homopolymers such as enantiomeric P(2HB) and P(2H3MB) SCs 8 and lactic acidbased random copolymers, 8,65,73,74 excluding those of enantiomeric poly(lactic acid-alt-glycolic acid) 15 and poly(lactic acidalt-2-hydroxybutanoic acid) 16 SCs. It is noteworthy that this is the first report for SC formation between enantiomeric SPCPs.…”

“…PLLA-b-PDLLA and PDLA-b-PDLLA are block copolymers of PLLA and PDLLA and of PDLA and PDLLA, respectively. other hand, we synthesized enantiomeric poly(L-lactic acid-altglycolic acid) and poly(D-lactic acid-alt-glycolic acid) alternating copolymers 15 and enantiomeric poly(L-lactic acid-alt-L-2hydroxybutanoic acid) and poly(D-lactic acid-alt-D-2-hydroxybutanoic acid) alternating copolymers 16 using the method developed by Meyer and co-workers 57−60 and found SC formation between two sets of enantiomeric polymer pairs by wide-angle X-ray diffractometry (WAXD) and DSC. The latter for enantiomeric poly(L-lactic acid-alt-L-2-hydroxybutanoic acid) and poly(D-lactic acid-alt-D-2-hydroxybutanoic acid) alternating copolymers is the first report for SC formation between enantiomeric alternating copolymers having two different types of chiral centers.…”

“…The latter for enantiomeric poly(L-lactic acid-alt-L-2-hydroxybutanoic acid) and poly(D-lactic acid-alt-D-2-hydroxybutanoic acid) alternating copolymers is the first report for SC formation between enantiomeric alternating copolymers having two different types of chiral centers. 16 Also, Takojima et al and Lue et al synthesized poly(L-lactic acid-alt-glycolic acid) alternating copolymers using organocatalytic ring-opening polymerization of methylglycolides. 62,63 Takojima et al also synthesized poly(D-lactic acid-alt-glycolic acid) and observed SC formation between the synthesized enantiomeric alternating copolymers.…”

“…Biobased and biodegradable poly­( l -lactide) or poly­( l -lactic acid) (PLLA) (Figure ) has balanced mechanical properties, high biocompatibility, and very low toxicity appropriate for a wide range of daily necessaries and environmental, biomedical, and pharmaceutical applications . Stereocomplex (SC) formation of PLLA with its enantiomeric polymer, i.e., poly­( d -lactide) or poly­( d -lactic acid) (PDLA) (Figure ), is effectively utilized to widen its applications, since SC formation between enantiomeric polymers such as PLLA and PDLA homopolymers normally enhances mechanical properties and thermal and hydrolytic degradation resistance of polylactide- or poly­(lactic acid) (PLA)-based materials. − With regard to poly­(α-substituted 2-hydroxyalkanoic acid)­s, not only enantiomeric PLLA and PDLA homopolymers but also enantiomeric lactic acid- or lactide-based random, alternating, and block copolymers − and enantiomeric substituted lactic acid-based homopolymers such as poly­(2-hydroxybutanoic acid) [P­(2HB)], poly­(2-hydroxy-3-methyl­butanoic acid) [P­(2H3MB)], and poly­(mandelic acid) (PMA) − were synthesized, and their SC crystallization was reported. However, as far as we are aware, synthesis and SC formation of enantiomeric stereo periodical copolymers (SPCPs) have not been reported so far, despite the expectation that their various stereosequences and SC formation can afford a wide variety of physical properties and biodegradation behavior and rate of PLA-based materials.…”

Boosting PLA melt strength by controlling the chirality of co-monomer incorporation

“…α-Hydroxybutyric acid, the precursor to diethylglycolide, is naturally produced in mammalian hepatic tissues. 66 (Bio)chemical syntheses of this hydroxy acid are known, starting from naturally occurring compounds such as α-ketobutyric acid, 67 l -threonine, 68 alpha-aminobutyric acid 69 or methyl vinyl glycolate. 70 Although chemical syntheses by reacting butyraldehyde with NaClO or by heating α-bromobutyric acid with formamide 71 are probably the main routes at the moment, biotechnological routes to obtain α-hydroxybutyric acid seem feasible.…”