In general, when a crystal is molten, all molecules forget about their mutual correlations and long-range order is lost. Thus, a regrown crystal does not inherit any features from an initially present crystal. Such is true for materials exhibiting a well-defined melting point. However, polymer crystallites have a wide range of melting temperatures, enabling paradoxical phenomena such as the coexistence of melting and crystallization. Here, we report a self-seeding technique that enables the generation of arrays of orientation-correlated polymer crystals of uniform size and shape ('clones') with their orientation inherited from an initial single crystal. Moreover, the number density and locations of these cloned crystals can to some extent be predetermined through the thermal history of the starting crystal. We attribute this unique behaviour of polymers to the coexistence of variable fold lengths in metastable crystalline lamellae, typical for ordering of complex chain-like molecules.

We report dynamic Monte Carlo simulations of polymer crystallization confined in thin films of thicknesses comparable to the polymer-coil sizes. We considered two contrasting affinities of the walls to the polymers, namely sticky walls that arrest the movement of polymers in contact with the substrate (such adsorbed layers allow to avoid dewetting) and slippery walls reflecting neutral repulsion of polymers. We found that at high temperatures slippery walls slightly enhance the crystallization rate with the decrease of film thickness, and the surface-assisted crystal nucleation results in dominant edge-on lamellar crystals (chain axis parallel to the wall); on the contrary, sticky walls significantly depress the crystallization rate, and the random crystal nucleation yields preferentially flat-on lamellar crystals (chain axis normal to the wall). The growth of self-seeded crystals demonstrates that the flat-on dominance is a kinetic phenomenon due to a stronger restriction on the thickening growth of edge-on lamellar crystals.