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We report that the anionic polymerization of P-mesityl and m-xylyl-substituted phosphaalkenes follows an unusual addition-isomerization mechanism. Specifically, the polymerization of ArP═CPh2 [Ar = Mes (1a), m-Xyl (1b)] involves the hindered nucleophilic anion intermediate, Ⓟ-P(Ar)-CPh2-, which undergoes a proton migration from the o-CH3 of the Mes/m-Xyl moiety to the −CPh2 moiety to afford a propagating benzylic anion. This mechanism is supported by the preparation of model compounds MeP(CHPh2)-4,6-Me2C6H2-2-CH2-CPh3 (2a) or MeP(CHPh2)-6-MeC6H3-2-CH2-CPh3 (2b), which were both crystallographically characterized. Polymerization of 1a or 1b in THF solution using n-BuLi (2 mol %) revealed 1H and 13C NMR signals assigned to −CH2- and −CHPh2 groups consistent with an addition-isomerization polymerization mechanism to afford poly(methylenephosphine) 3a or 3b. A large kinetic isotope effect (≤23) was determined for the n-BuLi-initiated polymerization of 1a-d9 compared to 1a in THF at 50 °C, consistent with C-H (or C-D) activation as the rate-determining step. This C-H activation step was modeled using DFT computations which revealed that the intramolecular proton transfer from the o-CH3 of the Mes moiety to the −CPh2 moiety has an activation energy (Ea = +18.5 kcal mol-1). For comparison, this computational value was quite close to the experimentally measured activation energy of propagation ArP═CPh2 in THF [Ea = 14.0 ± 0.9 kcal mol-1 (1a), 15.6 ± 2.8 kcal mol-1 (1b)]. [ABSTRACT FROM AUTHOR]

The flame retardant properties of paper coated with either poly(methylenephosphine) ( PMP) or poly(methylenephosphine oxide) ( PMP-O) are evaluated. Paper sheets made from thermomechanical pulp were coated with PMP ( Mn = 27,000 g mol−1, polydispersity index (PDI) = 1.47), PMP-O ( Mn = 30,000 g mol−1, PDI = 1.24), or monobasic ammonium phosphate (MAP) to achieve an approximate loading of 0.8 mmol P/g paper. Thermal stability studies by thermogravimetric analysis show that the paper degrades in two main stages, with the second thermo-oxidative stage having a slower rate of degradation for paper treated with flame retardants. The flame retardancy of the sheets was evaluated by Technical Association of Pulp and Paper Industry Standard Method T461 cm-00 and by limiting oxygen index (LOI) according to ASTM D2863. After leaching with water, samples coated with PMP or PMP-O show no loss of flame retardancy, while those coated with MAP lose all flame retardancy. The LOI of paper coated with PMP (23.1%) or PMP-O (25.9%) is higher than those of uncoated paper (19.6%), but lower than MAP-coated paper (34.7%). Analysis of the char provided evidence that the flame retardant mechanism of PMP and PMP-O involves the formation of phosphorus oxides and acids. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]