Poly‐β‐amides

Abstract

High molecular weight poly-p-amides with fiber-forming properties (repeating unit -N H -C R Z -C R~-C O -) differ from the polyamides of the nylon series in that the amide groups are much more closely spaced. These polymers are thus the nearest of the synthetic polyamides to natural silk. The production of poly-p-amides was made possible by a recent synthesis of p-lactams from olefins and chlorosulfonyl isocyanate. The anionic polymerization of the p-lactams gives poly-p-amides containing up to 10 000 monomer units in the chain. The molecular weight can be controlled as desired by means of initiators and chain terminators, and the properties can be varied within wide limits by the choice of the p-lactam or by copolymerization of several p-lactams. Remarkable differences are observed between polymers containing structural units in the threo form and those containing erythro structural units. The poly-p-amides can be spun into fibers having valuable textile properties.

Basic conformers in ?-peptides

“…Early attempts to realize ordered peptide structures with ␤-amino acids stem from the end of the 1960s and were continued in the 1970s and 1980s. 11,12,[17][18][19][20][21][22][23] After a more speculative hint on the possibility of helical conformations in ␤-peptides, 23 the first x-ray data indicating such structures were obtained in the early 1980s on poly(␣-isobutyl-L-aspartate). 11,12 In the meantime, various right-and left-handed helix types, as for instance 13 4 -, 3 1 -, 4 1 -, 7 2 -, and 5 2 -helices, were suggested and some of them confirmed on the basis of x-ray and nmr data.…”

Synthesis and characterization of poly(4-alkyl-4-methyl-2-azetidinone)s

“…The difference of 1.1 Å observed between the two values is reasonable; it corresponds to the additional methylene group between two sheets. Finally, if the 4.7 Å additional reflection, seen on the X-ray pattern of poly(MeMA) only, can be attributed to the (020) spacing, it is taken as the distance between adjacent chains linked by hydrogen bonds (b/2), corresponding to a unit cell b equal to 9.4 Å, close to that obtained by Bestian 4 for similar polymers. The b value of poly(EtMA) should be similar since the structure of the sheet is not influenced by the size of the substituents.…”

“…These results indicate that the racemic poly(4-alkyl-4-methyl-2-azetidinone)s are semi-crystalline when the alkyl substituent is a methyl or an ethyl group, as observed by Graf et al 3 for poly(4,4-dimethyl-␤-lactam), but are amorphous when it is a propyl, butyl, or pentyl group, in agreement with the results of Bestian. 4 Let's recall that the gels formed during the synthesis of poly(MeMA) and poly(EtMA) were opaque whereas the others were transparent. The amorphous behavior of racemic poly(PrMA), and of the corresponding butyl-and pentyl-substituted polymers, can be explained by the difference in size between the two substituents which impedes the crystallization due to the absence of chain regularity.…”

“…2 For example, Graf et al, 3 Bestian, 4 and Schmidt 5 studied the polymerization of a series of mono-, bi-, triand tetra-substituted 2-azetidinones, and the properties of the resulting polymers. Their chemical resistance and melting temperature depend on the chain stereoregularity and the nature of the substituents.…”

A Theoretical Study of <i>β</i>-Amino Acid Conformational Energies and Solvent Effect

“…Early attempts at realizing ordered peptide structures with β-amino acids dated from the end of the 1960s and were continued in the 1970s [1]- [3]. In 1994, Dado and Gellman studied the intramolecular hydrogen bonding properties of β-and γ-amino acid derivatives [4].…”