Synthesis of high-performance telechelic oligo(2,6-dimethylphenylene ether)s from limonene-based bis(2,6-dimethylphenol) core

Abstract

As the global demand for high-frequency communication materials grows alongside increasing environmental awareness, the need for low-dissipation polymers derived from renewable resources becomes ever more urgent. In this study, a novel limonene-derived bis(2,6-dimethylphenol) (LN-core) was synthesized via Friedel–Crafts alkylation and employed as a bio-based building block for oligo(phenylene oxide) (LN-OPE). The resulting oligomer was further functionalized with different crosslinkable end groups, yielding a series of telechelic OPEs: LN-PM (phenyl methacrylate), LN-VB (vinylbenzyl ether), and LN-VBz (vinylbenzoate). After thermal curing, these materials were evaluated in terms of thermal stability, hydrophobicity, moisture uptake, and dielectric performance, and benchmarked against commercial telechelic OPEs (SA9000 and OPE-2St). Notably, the LN-PM thermoset achieved a glass transition temperature (T_g) of 228 °C, 5 % weight-loss temperature (T_d5%) of 478 °C, a water contact angle (WCA) of ∼90.3°, water absorption (A_w) of ∼0.37 %, a dielectric constant (D_k) of 2.59, and a dissipation factor (D_f) of 0.0031, which closely matches the performance of SA9000. While the current bio-based content is modest, the introduction of a limonene-based core offers a unique molecular structure that avoids existing patent restrictions from major producers such as SABIC and MGC. This work sets the stage for future development of high-performance telechelic OPEs with significantly higher renewable content.