The effect of post-spin drawing on spider silk microstructure: a birefringence model

Measurements of optical birefringence have been used to characterise the effect of mechanical history on supramolecular structure in major ampullate silk from Nephila clavipes (golden orb weaver) spiders. Birefringence modelling is demonstrated to be a powerful technique for obtaining quantitative information on supramolecular rearrangement in response to macroscopic strain. Temporary and permanent birefringence changes measured as a function of strain and strain rate are interpreted in terms of two types of microstructural response: increased molecular alignment in all the microstructural phases present is accompanied by decreased lateral register within crystallographically ordered phases. Significant implications of these studies for the commercial processing of silks and silk-like biopolymers are discussed.