Poly‐α‐amino acid fibres

Poly‐α‐amino acid fibre being rich in β‐form has a silky quality. The fibre being rich in α‐form becomes woolly. When there is a strong interaction force through side chains of poly‐α‐amino acid molecules, the polymer solution is not spinnable regardless of the film forming ability. As it is difficult to spin a strong fibre directly from a polymer in α‐form, the spinning solution should contain some parts of random coil in the α‐form and the fibre molecules should be oriented in a parallel with the axis by stretching. Finally, most of the remaining β‐ or random‐parts should be retransformed into the α‐form. The β‐form of poly‐L‐alanine is most stable and most analogous to silk, but most of β‐form in poly‐L‐leucine stretched fibre is transformed into the α‐form in boiling dioxane and the woolly character appears. The character of poly‐α‐amino acid fibres seems to depend on the contents of α‐ and β‐form. Poly‐L‐leucine fibre in the α‐form is stable in boiling water and it seems to be unnecessary to introduce a cystine bridge into the fibre to maintain a woolly character. By copolymerizing a small amount of methionine into a polymer, the dyeability of fibres is remarkably improved.