Summary: Polystyrene‐block‐poly(methyl methacrylate) nanorods were prepared by wetting ordered porous alumina templates. We systematically investigated the diameter‐dependence of their morphologies by varying the pore diameters of the templates from 400 nm down to 25 nm. If the pore diameter exceeds the period of the block copolymer, the pores accommodate a non‐integer number of repeat periods. In case of smaller pores the occurrence of an ordered state could not be unambiguously verified.

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Lamellae-forming styrene/butadiene star block copolymers are studied to investigate the influence of morphology on micromechanical deformation mechanisms and mechanical properties by using transmission electron microscopy and tensile testing. A large homogeneous plastic deformation of polystyrene (PS) lamellae is found in styrene/butadiene star block copolymers on the basis of the new mechanism called thin-layer yielding. This mechanism depends strongly on the thickness of the PS lamellae. At a critical thickness of PS lamellae of about 20 nm, a transition from thin-layer yielding mechanism to a crazelike deformation was observed. These new deformation zones are similar to crazes with respect to their propagation perpendicular to direction of external stress and similar to shear bands with respect to an internal shear deformation component of the lamellae in the deformation zones. As a result of our investigations, the mechanical properties of star block copolymers can be understood in correlation with morphology and micromechanical deformation mechanisms.

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