Synthesis and fractionation of poly(phenylene methylene)

ABSTRACT 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 (CH2) 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 High molar mass poly(phenylene methylene) (Mn up to 60,000 g mol–1) was achieved by an optimized polymerization of benzyl chloride with SnCl4 or FeCl3 as a catalyst, followed by subsequent fractionation of the polymer. End group analysis by NMR spectroscopy revealed that the polymerization proceeds via a step growth mechanism. This first isolation of high molar mass PPM facilitates the search of potential applications of PPM.