Microwave-assisted Diels–Alder polycondensation of proton conducting poly(phenylene)s

Abstract

A 24-fold reduction in reaction time is achieved in the preparation of sulfonated poly(polyphenylene)s using microwave synthesis.

Semi‐fluorinated polyarylenes: Microwave‐assisted synthesis and structure–property relationships

“…The hydrogen atoms at each end of the newly formed phenyl groups from the Diels–Alder polymerization, which are a mixture of para and meta isomers, are found between 6.54 and 6.78 ppm. In the signals assigned to the central aromatic ring of the bistetracyclone monomer, the m–m peak is present at 6.34 ppm, the p – p peak is present at 6.27 ppm, and the p–m peak is present at 6.20 ppm 31,43 . The m–m and p–m peaks are similar in integrated area indicating a roughly equal mixture while the p – p peak has the largest integrated area and thereby is the primary component in the polymer conformation.…”

“…The CD(H)Cl 3 peak is present at 7.26 ppm in all spectra. The signal for the central aromatic ring from the starting material bistetracyclone appears as a triplet‐like peak between 6.0 and 6.5 ppm, and indicates the ratio between the three possible backbone Diels–Alder product conformations: meta–meta ( m–m ), para–para ( p – p ), and para–meta ( p–m ) 31,43 . The spectral peaks are relatively sharp for high molecular weight polymers, which can be largely attributed to the regular conformation among the repeat units.…”

“…Microwave‐assisted polymer synthesis and curing were reported a few years later, 39,40 with benefits including accelerated curing times, reduced reaction times, and in some cases increased yield. Step‐growth polymerization has been most commonly studied with microwave heating, and the synthesis of polyesters (polylactic acid and aliphatic polyesters) was 10 times faster compared to conventional oil bath heating, 41,42 and 24 times faster with sulfonated poly(phenylene)s 43 …”

Effect of steric constraints on the physico‐electrochemical properties of sulfonated polyaromatic copolymers

“…[23][24][25] Within this subset of aromatic-hydrocarbon-based PEMs exists a multitude of synthetic strategies to obtain various chemical architectures from comparatively lowcost starting materials. Common examples include sulfonated derivatives of poly(arylene ether sulfone)s, [26][27][28][29] poly(ether ether ketone)s, 13,30 poly(phenylene oxide)s, 31 poly(benzimidazole) s, [32][33][34][35] poly(imide)s 36 and poly(phenylene)s. [37][38][39][40][41][42] Of the numerous hydrocarbon-based structures examined in the literature to date, recent developments on sulfonated poly(phenylene)s have been particularly promising. These polymers, which are composed wholly of aryl-aryl linkages devoid of labile heteroatomic linkages, are potentially more resilient to oxidative degradation than other hydrocarbon PEMs, both ex situ 25,37,38,40,41 and in situ.…”

“…Membranes simultaneously possessing sufficient chemical and mechanical stability, water sorption characteristics, and electrochemical performance are close to realization. 2,15,39,40,[48][49][50] For example, a recent report detailed the synthesis and characterization of a well-defined, prefunctionalized sulfonated poly(phenylene) homo-polymer sPPP-H + via Diels-Alder polymerization. 38 While in situ fuel cell measurements revealed up to six times higher proton conductivity than Nafion®, the polymer swelled excessively and eventually dissolved at elevated temperatures.…”