화학공학소재연구정보센터
Macromolecules, Vol.52, No.13, 4949-4956, 2019
Monodisperse and Telechelic Polyethylenes Form Extended Chain Crystals with Ionic Layers
We report the synthesis of ionic telechelic low molecular -weight polyethylenes (PEs) with precise chain lengths that are derived from plant oils along with their morphologies and temperature-dependent ionic conductivities. Starting from the C-48 telechelic dimethyl ester, or the C-23 analogue for comparison, different ionic carboxylate end groups (H+, Na+, Cs+, Zn2+) were introduced by microwave-assisted saponification chemistry. Because of the precise length of the polymethylene sequence, these difunctional telechelic PEs crystallize into exceptionally well-ordered nanoscale-layered structures at room temperature. As a consequence of their extended chain crystal nature, the layer thickness is directly encoded by the telechelic molecules methylene chain length. Notably, C-21 ( COONa)(2), C-46(COONa)(2), and C-46(COOCs)(2) exhibit transitions in the crystalline structure prior to the fully disordered melt state, as evidenced by differential scanning calorimetry and in situ X-ray scattering. The melting transition is typically accompanied by a transition from layered ionic nanoaggregates between the crystallites to disordered ionic aggregates, with an interesting exception wherein the ionic layers transform to hexagonal symmetry. The temperature-dependent ionic conductivities of layered crystalline morphologies in the C-48 materials exhibit an Arrhenius-like behavior, indicating a decoupling from the slower polymer segmental motions at T < T-m. These new precise ionic telechelic PEs produce well-defined nanoscale-layered morphologies with tunable ion transport properties that could be further developed as solid-state electrolytes.