Strain dependent structural changes of spider dragline silk

Spider dragline silk is a natural semicrystalline polymer that is well-known for its unusual combination of tensile strength and extensibility. However, the correlation between structure and mechanical properties is still largely unknown. We have investigated the changes of the fiber's structure as probed by single fiber X-ray diffraction using a microfocus synchrotron beam, under controlled simultaneous mechanical load and variation of the humidity. Crystallite orientation, size, and lattice constants have been monitored while pulling the fibers.