Molecular Dynamics and Phase Separation in Co-crystal of Crystalline/Crystalline Polymer Blend

Semicrystalline polymers are categorized as either mobile or fixed crystals, depending on chain mobility in the crystalline region. In this work, we for the first time investigate molecular dynamics and phase structure in the co-crystal consisting of fixed and mobile polymer crystals by solid-state (ss) NMR spectroscopy. It is demonstrated that i) mobile component begins large amplitude motions associated with crystal-crystal transition while fixed ones keep their rigidity in the co-crystals and ii) asymmetric molecular dynamics leads to nano-segregations into mobile- and fixed-rich domains in the co-crystal below melting temperature (T_m). The observed phase separation induced by asymmetric molecular dynamics is similar to phase separation of miscible amorphous polymer blend, however, is limited to two-dimension due to parallel packing of stems inside the co-crystal as well as chain connectivity at the crystalline-amorphous boundary.