Heterostereocomplexation between Biodegradable and Optically Active Polyesters as a Versatile Preparation Method for Biodegradable Materials

Abstract

The thermal properties and crystallization of biodegradable and optically active poly[(S)-2-hydroxybutyrate] [P(S-2HB)], poly(l-lactide) (PLLA), poly(d-lactide) (PDLA) and their blends were investigated. The results of differential scanning calorimetry, wide-angle X-ray scattering (WAXS), and polarized optical microscopy first indicated heterostereocomplexation between biodegradable and optically active polyesters having different chemical structures and opposite configurations, that is, P(S-2HB) and PDLA. The melting temperature of the heterostereocomplex was higher than those of pure polymers. Such cocrystallization was not observed for P(S-2HB)/PLLA blends having identical configurations. The WAXS profile of P(S-2HB)/PDLA heterostereocomplex was very similar to those of the PLLA/PDLA and P(S-2HB)/P(R-2HB) homostereocomplexes and each crystalline diffraction peak of the heterostereocomplex was located between those of the homostereocomplexes. The present study strongly suggests that heterostereocomplexation will provide a novel versatile method for preparing biodegradable polyester materials with a wide range of physical properties and biodegradability.

Cocrystallization of monomer units in lactic acid-based biodegradable copolymers, poly(l-lactic acid-co-l-2-hydroxybutanoic acid)s

“…However, cocrystallization is not reported for the blend composed of L-(or D)-P(2HA) polymers with different types of side chains and same configurations and the block P(2HA) copolymer with L-(or D-) segments with different types of side chains and same configurations. In poly(L-lactide) [i.e., poly(L-lactic acid), PLLA]/poly(L-2-hydroxybutanoic acid) [P(L-2HB)] blend [31] and poly(D-2-hydroxybutanoic acid) [P(D-2HB)]-b-poly(D-lactide) [poly(D-lactic acid), PDLA] [32], respectively separate homo-crystallization of constituent polymers and sole homo-crystallization of PDLA segments occurred.…”

Stereocomplex crystallization and homo-crystallization of enantiomeric substituted poly(lactic acid)s, poly(2-hydroxy-3-methylbutanoic acid)s

“…P(L-2H3MB) and P(D-2H3MB) were synthesized by the polycondensation of (S)-and (R)-2-hydroxy-3-methylbutanoic acids (2-hydroxy-3-methylbutyric acids or α-hydroxyisovaleric acids) (≥99 and 98 %, respectively, Sigma-Aldrich, Japan K.K., Tokyo, Japan), respectively, were carried out at 130°C in the presence of p-toluenesulfonic acid (5wt% of monomer, monohydrate, guaranteed grade, Nacalai Tesque Inc., Kyoto, Japan) as a catalyst, according to a previously reported method [11,15,31,32]. The reaction times of the first and second step polycondensation under atmospheric and reduced (1.7-1.8 kPa) pressure were 5 and 13 h, respectively.…”

“…10 µm) were prepared by solution casting according to a previously reported method [11,15]. Each solution of the purified and vigorous stirring.…”

“…Hetero-stereocomplex is formed between L-and D-forms (and vice versa) of PLA and P(2HB) [15][16][17][18] and those of P(2HB) and P(2H3MB) [19]. Also, ternary and quaternary SC formation is reported to take place in ternary [P(D-2H3MB)] blends [22].…”

Crystallization and hydrolytic/thermal degradation of a novel stereocomplexationable blend of poly(L-2-hydroxybutyrate) and poly(D-2-hydroxybutyrate)

“…From the results reported for PLLA/PDLA blends, [16][17][18][19][20] it is expected that the resistance of P(L-2HB)/P(D-2HB) blends to hydrolytic and thermal degradation should be higher than those of pure P(L-2HB) and P(D-2HB). Moreover, optically pure P(2HB) can form a heterostereocomplex with non-substituted PLA having a configuration opposite to that of P(2HB), 22 whereas optically pure phenyl-substituted PLA is reported to have a higher intermolecular interaction with non-substituted PLA having a configuration opposite to that of phenyl-substituted PLA. 23 However, to the best of our knowledge, there are no detailed reports on the crystallization or hydrolytic and thermal degradation behavior of P(L-2HB)/P(D-2HB) blends, although such information is crucial for designing and processing biodegradable stereocomplexationable P(L-2HB)/P(D-2HB) blends for biomedical, pharmaceutical and environmental applications.…”