Asymmetric Molecular Dynamics and Anisotropic Phase Separation in the Cocrystal of the 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 investigate molecular dynamics and phase structure in the cocrystal consisting of fixed and mobile polymer crystals by solid-state (ss) nuclear magnetic resonance (NMR) spectroscopy. It is demonstrated that (i) the mobile component begins large amplitude motions associated with crystal-crystal transition, while fixed ones keep their rigidity in the cocrystal, and (ii) asymmetric molecular dynamics leads to nanosegregations into mobile- and fixed-rich domains in the cocrystal below the melting temperature (T-m). The observed phase separation induced by asymmetric molecular dynamics is similar to the phase separation of the miscible amorphous polymer blend; however, it is limited to two dimensions due to the parallel packing of the stems inside the cocrystal, as well as chain connectivity at the crystalline-amorphous boundary.

Automated summary

This study investigates the molecular dynamics and phase structure of a cocrystal consisting of fixed and mobile polymer crystals using solid-state nuclear magnetic resonance (NMR) spectroscopy. It is found that the mobile component undergoes large amplitude motions associated with crystal-crystal transition, while the fixed component remains rigid in the cocrystal. Asymmetric molecular dynamics leads to nanosegregations of mobile- and fixed-rich domains in the cocrystal, similar to phase separation in miscible polymer blends, but limited to two dimensions due to the packing and connectivity in the cocrystal.