High Dielectric and Mechanical Properties Achieved in Cross-Linked PVDF/α-SiC Nanocomposites with Elevated Compatibility and Induced Polarization at the Interface

Remarkably improved dielectric properties including high-k, low loss, and high breakdown strength combined with promising mechanical performance such as high flexibility, good heat, and chemical resistivity are hard to be achieved in high-k dielectric composites based on the current composite fabrication strategy. In this work, a family of high-k polymer nanocomposites has been fabricated from a facile suspension cast process followed by chemical cross-linking at elevated temperature. Internal double bonds bearing poly­(vinylidene fluoride-chlorotrifluoroethylene) (P­(VDF-CTFE-DB)) in total amorphous phase are employed as cross-linkable polymer matrix. α-SiC particles with a diameter of 500 nm are surface modified with 3-aminpropyltriethoxysilane (KH-550) as fillers for their comparable dielectric performance with PVDF polymer matrix, low conductivity, and high breakdown strength. The interface between SiC particles and PVDF matrix has been finely tailored, which leads to the significantly elevated dielectric constant from 10 to over 120 in SiC particles due to the strong induced polarization. As a result, a remarkably improved dielectric constant (ca. 70) has been observed in c-PVDF/m-SiC composites bearing 36 vol % SiC, which could be perfectly predicted by the effective medium approximation (EMA) model. The optimized interface and enhanced compatibility between two components are also responsible for the depressed conductivity and dielectric loss in the resultant composites. Chemical cross-linking constructed in the composites results in promising mechanical flexibility, good heat and chemical stability, and elevated tensile performance of the composites. Therefore, excellent dielectric and mechanical properties are finely balanced in the PVDF/α-SiC composites. This work might provide a facile and effective strategy to fabricate high-k dielectric composites with promising comprehensive performance

Organocatalyzed Photoredox Polymerization from Aromatic Sulfonyl Halides: Facilitating Graft from Aromatic C–H Bonds

Aromatic sulfonyl halides are readily accessible from many sources. With newly synthesized <i>N</i>-aryl­phenothiazine catalysts, organocatalyzed photoredox polymerization has been developed with arylsulfonyl halides initiators using white or purple LEDs light sources. This method allows the preparation of poly­(meth)­acrylates and poly­(meth)­acrylamides possessing a broad scope of (hetero)­aryl chain ends without metal-contamination concern. Investigations such as MALDI-TOF analysis, chain extension, and “ON/OFF” control experiments confirmed the fidelity of the polymer structure and reliability of this method. Moreover, this method facilitates the two-step preparation of brush polymers from polystyrene through an electrophilic aromatic substitution/organocatalyzed photopolymerization sequence