Comb-like ionic complexes, nATMA . PG(DL)GA, were prepared from microbial poly(gamma-glutamic acid), with a nearly racemic configuration, and alkyltrimethylammoniun bromides, with linear alkyl chains containing an even number of carbon atoms, n, ranging from 12 to 22. The complexes had a nearly stoichiometric composition, displayed thermal stability up to temperatures above 200 degrees C and were insoluble in water but soluble in organic solvents. In the solid state, they were arranged in a regularly layered structure with the alkyl side chain crystallized for n > or = 18. Heating above melting entailed a contraction in the interlayer distance which varied from 1 to 10% depending on the value of n. Comparison with data reported on similar complexes obtained from nearly enantiomerically pure poly(gamma-glutamic acid) revealed an overall behavior very similar for the two series but with specific significant differences concerning side chain crystallinity and dimensional response to temperature.
The synthesis of 2,3-disubstituted poly(β-peptide)s (nylon-3 analogues) bearing the benzyloxy
group at position 3 and the diethoxymethyl or the isobutoxycarbonyl group at position 2, is described.
Both optically pure and racemic forms were prepared for each case and all them were characterized by
standard methods. The structure of these poly(β-peptide)s was preliminary examined by X-ray diffraction
and infrared spectroscopy. It was concluded that they do not tend to adopt the α-helixlike conformation
characteristic of poly(β-l-aspartate)s but rather a contracted conformation with amide groups in the
nonassociated state.
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