<p>The morphologies of self-assemblies comprising block copolymers are key to their applications. In this regard, crystallization-driven self-assembly is a potent strategy for the precise fabrication of low-dimensional anisotropic structures. However, few reports have discussed kinetically controlled morphologies. Herein, we found that poly(<i>N</i>-butylglycine)-<i>b</i>-poly(sarcosine) formed spherical self-assemblies, and phase-transitioned to nanosheets, and subsequently nanotubes, depending on the incubation time and temperature. We also noticed that the energy landscape associated with phase transition was affected by the length of the hydrophobic segment. These findings provide a foundation for the rational design of block copolymer for the preparation of purpose-built structures.</p> Graphical abstract <p></p>