Poly(alpha-alkyl gamma-glutamate)s of microbial origin. 2. On the microstructure and crystal structure of poly(alpha-ethyl gamma-glutamate)s.
The stereochemical microstructure and crystalline structure of nearly racemic poly(alpha-ethyl gamma,DL-glutamate) obtained by esterification of biosynthetic poly(gamma-glutamic acid) were examined by NMR, DSC, and powder X-ray diffraction. The two enantiomerically pure poly(alpha-ethyl gamma-glutamate)s, as well as the racemic stereocopolymers with random and alternating microstructure, were prepared by chemical synthesis and studied in parallel to help in the interpretation of the data. The (13)C NMR analysis revealed that biosynthetic poly(alpha-ethyl gamma,DL-glutamate) consists of a block stereocopolymer accompanied by minor amounts of a mixture of the two optically pure homopolymers. The polymer is crystalline, with a degree of crystallinity and crystal structure essentially similar to those displayed by the optically pure polymers but clearly different from the alternating copolymer. Conversely, the racemic stereocopolymer with a random microstructure prepared by chemical synthesis is amorphous. The crystal structure of the racemic mixture of the D- and L-homopolymers seems to be very close to that of the biosynthetic stereocopolymer, although some indications suggesting the existence of a stereocomplex were found.
Martínez de Ilarduya
Antxon
A
Departament d'Enginyería Química, Universitat Politécnica de Catalunya E.T.S. d'Enginyers Industrials de Barcelona, Diagonal 647, 08028 Barcelona, Spain.
Ittobane
Najim
N
Bermúdez
Marta
M
Alla
Abdelilah
A
El Idrissi
Mustafa
M
Muñoz-Guerra
Sebastián
S
D001419:Bacteria / Q000737:chemistry; D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D004951:Esterification; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D011099:Polyglutamic Acid / Q000737:chemistry*; D013237:Stereoisomerism; D014961:X-Ray Diffraction
D011099:Polyglutamic Acid