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Copoly(-alkyl γ,DL-glutamate)s containing octadecyl and dodecyl side chains in a wide range
of compositions (coPAAG-18,12) were synthesized from microbial racemic poly(γ,DL-glutamic
acid) (PGGA). Feed ratios of 1-octadecanol to 1-dodecanol were 100:0, 75:25, 50:50, 25:75,
and 0:100. The procedure of synthesis consisted of two-steps: Poly(-ethyl γ,DL-glutamate)
(PAAG-2) was prepared by esterification of PGGA and then transesterified with 1-octadecanol
or/and 1-dodecanol to obtain the corresponding copolymers coPAAG-18,12 (x:y).
The polyglutamates and copolyclutamates synthesized in this work were characterized by
Nuclear Magnetic Resonance (1H-NMR), Fourier Transform Infrared (FTIR), Gel Permeation
Chromatography (GPC) and Intrinsic Viscosity (IV). Their thermal properties were evaluated by
Thermogravimetry (TGA) and Differential Scanning Calorimetry (DSC).
These copolymers display the following features: a) First melting temperature (Tm
1) ( 50 oC)
according to antecedents; b) Second melting temperature (Tm
2) (~100 oC) striking and without
explanation; c) No melting temperature (Tm) in the case of PAAG-12; d) A Tm value in
copolyesters going down with the content in dodecanol units.
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