Poly(phenylene methylene) (PPM) exhibits pronounced blue fluorescence in solutions as well as in the solid state despite its non-p-conjugated nature. Optical spectroscopy was used to explore the characteristics and the physical origin of its unexpected optical properties, namely absorption in the 350-450 nm and photoluminescence in the 400-600 nm spectral regions. It is shown that PPM possesses two discrete optically active species, and a relatively long photoluminescence lifetime (>8 ns) in the solid-state. Given the evidence reported herein, p-stacking and aggregation/crystallization, as well as the formation of anthracene-related impurities, are excluded as the probable origins of the optical properties. Instead there is sufficient evidence that PPM supports homoconjugation, that is: p-orbital overlap across adjacent repeat units enabled by particular chain conformation(s), which is confirmed by DFT calculations. Furthermore, poly(2-methylphenylene methylene) and poly(2,4,6-trimethylphenylene methylene) -two derivatives of PPM -were synthesized and found to exhibit comparable spectroscopic properties, confirming the generality of the findings reported for PPM. Cyclic voltammetry measurements revealed the HOMO-LUMO gap to be 3.2-3.3 eV for all three polymers. This study illustrates a new approach to the design of light-emitting polymers possessing hitherto unknown optical properties.

Poly(phenylene methylene) (PPM) was isolated in a broad range of molar masses by optimization of the catalytic polymerization of benzyl chloride with SnCl4 or FeCl3, followed by fractionation by Soxhlet extraction or phase separation in concentrated solutions in poor solvents. Low molar mass products were also obtained by quenching the reaction at moderate monomer conversions. Products with number average molar masses (Mn) ranging from 200 to 61,000 g mol−1 were isolated, the latter being an order of magnitude above the previously reported values. DSC analysis of polymers of different molar masses revealed that the glass transition temperature follows the Flory‐Fox equation reaching a plateau value of 65 °C at a molar mass between 10,000 and 20,000 g mol−1. The onset of decomposition temperature of higher molar mass products proceeds above 450 °C (maximum decomposition rate at 515 °C), according to TGA. Furthermore, the substitution pattern of PPM was discussed by study of chemical shifts of the methylene group true(CH2true) by extensive NMR spectroscopy (1H, 13C, DEPT, and HSQC) and by comparison with two mono‐substituted derivatives of PPM—poly(2,4,6‐trimethylphenylene methylene) and poly(2,3,5,6‐tetramethylphenylene methylene)—which were synthesized analogous to PPM. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 309–318

Poly(phenylene methylene) (PPM) is a thermally stable, hydrophobic, fluorescent hydrocarbon polymer. PPM has been proposed earlier to be useful as a coating material but this polymer was isolated in relevant molar masses only recently, and in large quantities. Accordingly, the preparation of coatings based on PPM and their behavior was explored in this study, with the example of the metal alloy AA2024 as a common substrate for corrosion tests. Coatings free of bubbles and cracks were obtained by hot pressing and application of the following steps: Coating on AA2024 with a layer of polybenzylsiloxane to improve the adhesion between PPM and the metal surface, the addition of polybenzylsiloxane to PPM in order to enhance the viscosity of the molten PPM, and the addition of benzyl butyl phthalate as a plasticizer. Electrochemical corrosion tests showed good protection of the metal surface towards a NaCl solution, thanks to a passive-like behavior in a wide potential window and a very low current density. Remarkably, the PPM coating also exhibited self-healing towards localized attacks, which inhibits the propagation of corrosion.

Poly(phenylene methylene)s (PPMs) with high molar masses were isolated by polymerization of benzyl chloride catalyzed with tungsten(II) compounds and subsequent fractionation. Four different tungsten(II) catalysts were successfully exploited for the polymerization, for which a strict temperature profile was developed. The PPMs possessed roughly a trimodal molar mass distribution. Simple fractionation by phase separation of 2-butanone solutions allowed to effectively segregate the products primarily into PPM of low molar mass (Mn = 1600 g mol−1) and high molar mass (Mn = 167,900 g mol−1); the latter can be obtained in large quantities up to 50 g. The evolution of the trimodal distribution and the monomer conversion was monitored by gel permeation chromatography (GPC) and 1H NMR spectroscopy, respectively, over the course of the polymerization. The results revealed that polymerization proceeded via a chain-growth mechanism. This study illustrates a new approach to synthesize PPM with hitherto unknown high molar masses which opens the possibility to explore new applications, e.g., for temperature-resistant coatings, fluorescent coatings, barrier materials or optical materials.

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