Influence of Reaction Parameters on the Living Cationic Polymerization of Phosphoranimines to Polyphosphazenes

Abstract

A new approach to the synthesis of poly(dichlorophosphazene) and poly(organophosphazenes) has been developed via the cationic condensation polymerization of phosphoranimines. The effects of solvent, temperature, concentration, and initiator on the cationic condensation polymerization of Cl3PNSiMe3 and PhCl2PNSiMe3 are described. The ambient temperature polymerization of PhCl2PNSiMe3 is faster in toluene, benzene, and dioxane than in methylene chloride or chloroform. The polymerizations of Cl3PNSiMe3 and PhCl2PNSiMe3 were monitored by both NMR (31P and 1H) and GPC methods. The initial polymerization rates are slow, presumably because of the precipitation of phosphazene short chain salts, RCl2PN−[PR(Cl)N] n −PCl3 +PCl6 - (where R = Cl or Ph; n = 0, 1, 2, ...). After the chains redissolve (∼15−60 min), polymerization proceeds, with the propagation rates following pseudo-first-order kinetics for both monomers. The reactions in toluene, benzene, or dioxane yielded polymers with controlled molecular weights in the range of 105, with narrow polydispersities (<1.3). The usefulness of this approach for the synthesis of a biomedically important polyphosphazene has also been demonstrated.

Salt-in-Polymer Electrolytes for Lithium Ion Batteries Based on Organo-Functionalized Polyphosphazenes and Polysiloxanes

“…A particularly interesting method (last one in Table 1) was reported in 1997 consisting of a cationic living polymerization of phosphazene monomers with PCl 5 as chain growth initiator [27]. However, at the beginning, it was quite difficult to synthesize the monomeric phosphazene with the necessary purity according to the available procedures [28].…”

Progress in Synthesis of Polyphosphazenes

“…Up to now, the PDCP have been mainly prepared by thermal ring-opening or catalysis-solution polymerization of HCCPs or from phosphoranimine monomers via a controllable room temperature living ionic condensation process [7][8][9][10].…”

“…Allcock et al [1,9] first successfully synthesized a linear open-chain PDCP which can be dissolved in most organic solvent via thermal ring-opening polymerization of HCCP in 1965. When HCCP is in the molten state at about 250 • C under vacuum, it can be thermally ring-opening polymerized to prepare long-chain polymers and then the chlorine in the phosphorus atoms can be easily substituted by a nucleophilic substitution in a suitable solvent to obtain a functionalized polyphosphazenes.…”

Polyphosphazenes from Condensation Polymerization

“…In a short time, the method was extended to the synthesis of polymers with directly P-C-bonded groups [14], the ''living'' cationic ends of the polymer were used to prepare a variety of block copolymers [15], and studies showed that there is a relationship between initiator-monomer stoichiometry [16]. The capability of obtaining polymers with controllable narrow molecular weights is ultimately useful for biological applications since polymer properties are related to molecular weight [16]. The most recent advance in the synthesis of polyphosphazenes from Nsilylphosphoranimines is a result of efforts to form phosphoranimine cations stabilized by phosphine ligands [17].…”