Physical Gelation in a Triblock Copolymer Solution: In Situ Study of Stress−Strain Behavior and Structural Development

An in situ study of the microstructure and mechanical properties of polystyrene−poly(ethylene−butylene)−poly styrene (SEBS) triblock copolymer gels was performed. Simultaneous time-resolved synchrotron radiation X-ray scattering and stress−strain measurements at extensions up to λ = 2 indicate that the macroscopic deformations are transferred to a microscopic level via the three-dimensional network of microdomains. The deformation of the microstructure is nonaffine at low extension rates (4 × 10 -4 s -1 ) and becomes affine at higher rates (10 -2 s -1 ).