Spinning silk at Maidenhead: The polypeptide project

This paper reviews the research programme of the Maidenhead Laboratory of Courtaulds Ltd. devoted to the synthesis of textile fibres based on poly(alpha-amino acids), regarded as models for natural silk. The work involved studies of the preparation, properties and structures of the polymers and development of suitable fibre-spinning techniques. Polymers were prepared from N-carboxy-alpha-amino acid anhydrides (NCAs); the reactions involved, following initiation by protic or aprotic bases, are outlined. Applications of polarized infra-red radiation in elucidating polymer structure were pioneered at Maidenhead, and played a major role in the recognition of the alpha and beta modifications of poly(alpha-amino acids) and their similarities to the fibrous proteins. The two forms show differences in properties, notably solubility, arising from different patterns of hydrogen bonding. X-ray diffraction patterns of oriented fibres of beta-poly-L-alanine are remarkably similar to those of many silk fibroins. Solution-spinning is the only suitable process for fibre production from these polymers, and a novel method, permitting relatively high speeds, is described. Finished fabrics woven from 100 denier/60 filament yam of poly (gamma-methyl-L-glutamate) were found to possess many of the distinctive silk-like properties, together with a few additional easy-care features. Some costing details of the overall process are given; for 10 x 10(6) Ib per year production, L-glutamic acid costs just exceeded 30% of the total.