Poly‐β‐amides

AbstractHigh molecular weight poly‐β‐amides with fiber‐forming properties (repeating unitNHCR2CR2CO) 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‐β‐amides was made possible by a recent synthesis of β‐lactams from olefins and chlorosulfonyl isocyanate. The anionic polymerization of the β‐lactams gives poly‐β‐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 β‐lactam or by copolymerization of several β‐lactams. Remarkable differences are observed between polymers containing structural units in the threo form and those containing erythro structural units. The poly‐β‐amides can be spun into fibers having valuable textile properties.