ISSN:
1573-4900
Schlagwort(e):
Poly(lactide)
;
Alternating propylene-CO-copolymer
;
Stereocomplex
;
Powder diffraction
;
Force-field simulation
;
Poly(ethyleneglycol)
;
AB block copolymers
;
Atomic force microscopy
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Maschinenbau
Notizen:
Summary Both (−)- and (+)-poly(lactide) (PLA) crystallize into a stereocomplex with a melting point that is 50 °C higher than that of crystals of the same-handed enantiomers. According to Boyer et al. [Polym. Prepr., 36 (1995) 87] and Jiang et al. [J. Am. Chem. Soc., 117 (1995) 7037], alternating isotactic propylene-CO-copolymers (P(P-alt-CO)) also form a stereocomplex with a higher melting point (60 °C). Force-Field-simulated structures for both polymer systems were found to agree well with X-ray data, irrespective of whether they had a chiral or racemic packing. The almost similar results for both stereocomplexes indicate that they might form a mixed stereocomplex of (−)-PLA and (+)-P(P-alt-CO). In acetonitrile, both enantiomers of an AB block copolymer derivative, poly(lactide)-poly(ethyleneglycol) (PLA-PEG); were found to crystallize exclusively into a racemic lattice. The influence of racemic packing on self-assembly of the two-block copolymer was analyzed by atomic-force microscopy. An equimolar mixture of (−)- and (+)-PLA-PEG formed spherical particles through stereocomplexation, in contrast to chiral block copolymers that formed large crystal needles and long rods.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF01185672
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