Report No xxxx - Instytut Fizyki JÄ drowej PAN

STUDIES OF POLY(ASPARTIC ACID) STRUCTURE AND ITS
DERIVATIVES USING 1 H NMR SPECTROSCOPY
Elżbieta Tylek, Jolanta Polaczek, Jan Pielichowski
Department of Chemistry and Technology oh Polymers Technical University, Kraków, Poland
Poly(aspartic acid) ( here: PAA) belongs to biodegradable polymers, which could be have a
lineal or cyclic structure (figure 1). Poli(aspartates) have different proprieties depending on
th eir chemical construction [1,2].
O
N
NH
CH
CH 2
CO NH CH
CO
O
q
COOH
n
CH 2
m
q ≥ n+m
COOH
Figure 1. Structure poly(aspartic acid)
The structure of poly(aspartic acid) and its derivatives can be characterized using some
1
nuclear magnetic resonance methods; especially H NMR and 13 C NMR spectroscopy. The
main chain of PAA include α - and β - peptide bonds, where the ratio α:β peptide units can be
determined by NMR spectroscopy; particularly important are signals methane in 1 H NMR
and signals methylene in 13 C NMR. Application 1 H NMR spectroscopy can observe local
branches and opening peptide ring in PAA structure. Using 13 C NMR spectroscopy in PAA
and its derivatives to make possible can be determined local branches, characteristic
conformation and irregular structure.
Spectrum 1 H NMR of poly(succinimide) characterized signals of the methine proton in
5,3 ppm and smaller signal at 4,6 ppm succinimide units. Two very board resonance are
observed at 12,48 ppm and 13,22 ppm. The broad peaks between 8,0 and 9,5 ppm are
consistent with amide protons of branches or ring-open sites [3].
Process hydrolysis of the polymerization products leads to poly(aspartates) containing α- and
β-as partic acid units. This can be caused by attack of nucleophilic factor on bond C-N
in ring of succinimide. Possible is opening of ring succinoimide in position α- and β- what
opening in position β- is more prefer.
In result of hydrolysis can be obtained salts of poly(aspartic acid). On figure 2 shows
characteristic spectrum 1 H NMR of sodium polyaspartate in D 2 O. Signals of protons methine
(-CH-) and methylene (-CH 2 -) of the succinimide unit disappeard and appear signals of
protons methine at 4,7 and 4,2 ppm and methylene at 2.8, 2.7 and 2.4 ppm. Two different
chemical shifts have shown different openings of ring succinimide. The α/β ratio can be
determined by nuclear magnetic resonance spectroscopy and carries out 26 / 74 [4].
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