Research and development is currently underway to develop copper-clad laminates (CCL) that are suitable for the next era of ICT technology. This advancement is driven by the need for enhanced capacity and speed, essential for 5G and 5G millimeter wave communications.These cutting-edge communications rely on high-frequency bands, which increase electrical losses and generate heat then contained within CCL boards during processing. Consequently, there’s a risk of flexing or bending in the CCL,potentially leading to short circuits and fires. Thus, ensuring a high glass transition point (Tg) and incorporating flame retardant properties are imperative for CCL materials utilized in high-frequency communications. However, pursuing advanced CCL materials has been hindered by the trade-offs between achieving flame retardancy, maintaining low dielectricity, ensuring high Tg (heat resistance), and ensuring compatibility with flame retardant components.This paper aims to elucidate the mechanism behind flame retardancy and offer examples of flame-retardant lowdielectric compounds characterized by both low dielectricity and high Tg.

Phosphorus-containing polymeric materials have been extensively studied in both scientific and industrial fields due to their unique properties. Among the wide variety of the phosphorus-containing materials, this review focuses on the synthesis and properties of the polymeric materials containing phosphine sulfide (P=S) groups. Because the P=S group has some unique properties, such as good thermal and chemical stability, coordination ability to transition metals, high molar refraction, and low polarity, the polymers containing the corresponding groups have been applied to flame retardant materials, polymer ligands, high refractive index materials, low birefringent materials, and low dielectric materials, some of which exceed the performance of conventional phosphorus-containing polymeric materials. Moreover, network polymer materials containing P=S groups will be growing interest for their practical use in electronic and optical fields.

Bio-based bis-functional limonene cyclic carbonate (BLC) was synthesized in 95% yield by the reaction of bisfunctional epoxide (bis-trans-LO) and carbon dioxide at 3.0 MPa in the presence of tetra-n-butylammonium chloride for 21 h at 100 ºC. The cross-linking reaction between BLC and branched polyethyleneimine (BPEI) afforded polyurethane networks with glass transition temperature (Tg ) of -11.7 to 54.9 ºC in 34% to 90% yields as a methanol-insoluble part,which depends on the feed ratio of the primary amino group to the carbonate group ([carbonate group]0:[primary amino group]0=1:0.18, 1:0.37, 1:0.92, 1:1.8, 1:3.7 (mol:mol)). The good tensile strength (11.7, 13.0 MPa) and lap shear adhesive strength (22.4, 21.4 MPa) of the network polymer were achieved at [carbonate group]0:[primary amino group]0=1:0.92 and 1:1.8 (mol:mol), respectively.

Although lignopheols, which are linear-typed lignin derivative macromolecules with only small amount of random conjugations, showed light-beige appearances in powders and brown in solutions, almost no absorbance in visible light region > 400 nm. These appearances were produced by relaxation processes such as fluorescence influenced by inter-/intramolecular interactions. Differences in peaks between UV-Vis and excitation spectra strongly implied that there are widespread and multi-stepped relaxation processes. Analyses of energy transfers in the lignophenols compared to damaged alkali lignins with rich conjugations using ketones as energy acceptors were carried out by Stern-Volmer analysis. It is found that there are multi-stepped energy transfers in lignin macromolecules via located conjugations by comparison between UV-Vis and excitation spectra and by analyses of synchro fluorescence spectra. Especially hardwood lignophenol showed highest ability for energy transfers twice larger than softwood lignophenols.

Polymerization of anthracene dimers containing amino groups and epoxy compound was investigated with the aim of synthesizing the epoxy cured materials that can be crosslinked and decrosslinked by heating. Their application to dismantlable adhesives was also studied. As primary diamines capable of undergoing covalent bonds cleavage under heating, 9-aminoanthracene dimers (A(NH2)-D) and 2-(9-anthryl)ethylamine dimers (A(C2NH2)-D) were used. A (C2NH2)-D showed higher reactivity with epoxy compounds than A(NH2)-D due to smaller steric hindrance around the amino group. Furthermore, in comparison with the previously reported 9-anthracenecarboxylic acid dimers (A(CO2H)-D),the polymerization of A(C2NH2)-D with epoxy compounds proceeded at lower temperatures. As a result, the thermal dissociation of anthracene dimer units during polymerization was suppressed and the cured materials with a higher gel fraction was obtained. Decrosslinking took place by heating at higher temperatures than the polymerization temperature.Moreover, A(C2NH2)-D resulted in better compatibility with epoxy compounds compared to A(CO2H)-D. The epoxy cured materials with A(C2NH2)-D functioned as a dismantlable adhesive, exhibiting higher lap-shear adhesion strength and better dismantlability than that with A(CO2H)-D.