Exploring the Nanoscale Buckling of Lamellae-Forming Copolymer under Planar Tension

High Resolution Image Download MS PowerPoint Slide This study investigates the in situ evolution of nanoscale buckling in lamellae-forming copolymers subjected to planar stretching using a nanotensile holder. Transmission electron microscopy (TEM), combined with simulated projection images, is employed to investigate the nanoscale buckling behavior in the oriented lamellar triblock copolymer of polystyrene- b -polyisoprene- b -polystyrene (PS- b -PI- b -PS). When planar tension is applied perpendicular to the hard and soft layers in lamellae, transverse strain is constrained while thickness strain is contracted. This contraction causes the PI rubbery phase to exert a strong compressive stress on the PS phases due to the strong coupling between the two phases. As the strain increases, the contracted strain in the thickness direction eventually causes buckling instability, leading to a transition from lamellae to a chevron structure. Analyses of the lamellae-to-chevron transition using geometrical arguments align with the direct TEM image results. This study bridges the gap between discontinuous TEM observation and a continuous simulated model, providing a detailed mechanism for the strain state in lamellae.