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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]

A survey of the state-of-the-art in the development of synthetic methods to incorporate p-block elements into polymers is given. The incorporation of main group elements (groups 13–16) into long chains provides access to materials with fascinating chemical and physical properties imparted by the presence of inorganic groups. Perhaps the greatest impedance to the widespread academic and commercial use of p-block element-containing macromolecules is the synthetic challenge associated with linking inorganic elements into long chains. In recent years, creative methodologies have been developed to incorporate heteroatoms into polymeric structures, with perhaps the greatest advances occurring with hybrid organic–inorganic polymers composed of boron, silicon, phosphorus and sulfur. With these developments, materials are currently being realized that possess exciting chemical, photophysical and thermal properties that are not possible for conventional organic polymers. This review focuses on highlighting the most significant recent advances whilst giving an appropriate background for the general reader. Of particular focus will be advances made over the last two decades, with emphasis on the novel synthetic methodologies employed. [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]