A series of polyacrylonitrile-block-polystyrene (PAN-b-PS) and polyacrylonitrile-block-poly(methyl methacrylate) (PAN-b-PMMA) diblock copolymers with PAN volume fraction up to 20% self-assembles in nonpolar selective solvents to form cylindrical micelles with a PAN core, having contour length varying between less than 1 mu m and tens of micrometers. Micelle characterization by differential light scattering, nuclear magnetic resonance, transmission electron microscopy, atomic force microscopy and differential scanning calorimetry enabled to point out the role played by crystallinity during micellization, thence suggesting that the core crystallization force overcomes other factors governing self-assembling processes.