No abstract

A new method for the synthesis of poly(dichlorophosphazene) at ambient temperatures is described. It involves the initiation of Cl3PNSiMe3 with small amounts of PCl5 in CH2Cl2 to yield poly(dichlorophosphazene), (NPCl2) n , with narrow polydispersities. The molecular weight of poly(dichlorophosphazene) was controlled by altering the ratio of monomer to initiator. The polymer chains were found to be active after chain propagation since further addition of monomer resulted in the formation of higher molecular weight polymer. Integration of 1H and 31P NMR spectra of these reactions revealed that the polymerization follows first-order reaction kinetics with respect to monomer concentration. Active polymer chains may be quenched or end-capped by the addition of trace quantities of Me2(CF3CH2O)PNSiMe3 or (CF3CH2O)3PNSiMe3. Furthermore, PBr5, SbCl5, and Ph3C[PF6] were also found to be effective initiators in CH2Cl2 at room temperature.

An improved synthesis of the phosphazene polymerization precursors, hexachlorocyclotriphosphazene, (NPCl2)3 (1), and Cl3PNSiMe3 (2) is reported. The addition of PCl5 to N(SiMe3)3 in methylene chloride at 40 °C produced a mixture of phosphazenes which contained 76% of 1. However, the addition of N(SiMe3)3 to PCl5 in methylene chloride at 0 °C, followed by the addition of hexane, provided 2 in 40% yield. The mechanism of the reaction is discussed.

Two methods have been developed for the controlled formation of carboxylic acid units at the surfaces of aryloxyphosphazene high polymers. The first involves a permanganateinduced oxidation of p-methylphenoxy side groups, with the surface density of carboxylic acid units being controlled by the ratio of p-methylphenoxy to phenoxy groups along the polymer chains. The second approach involves a base-induced hydrolysis of carboxylate ester functions at the para-positions of surface aryloxy side groups. In this method the surface density of carboxyl units is controlled by the reaction conditions, especially by the temperature and the solvent for the base. The same ester functions were converted to alcohol moieties by surface reductions using lithium aluminum hydride in diethyl ether. The surface structures before and after these reactions were studied by a combination of contact angle measurements, X-ray photoelectron spectroscopy, scanning electron microscopy with X-ray microanalysis, and ATR-IR spectroscopy.

The cyclic carbophosphazene N3P2CCI5 undergoes thermal ring-opening polymerization at 120 °C to yield poly(pentachlorocarbophosphazene), [NgPgCCleln, as a hydrolytically sensitive elastomer. Treatment of this polymer in solution with primary and secondary alkylamines yielded poly(aminocarbophosphazenes) [NgPüCtNRiRü)^,, where Ri = H, R2 = nPr or 'Pr, and Ri = Ri = Me or Et. These polymers are also sensitive to moisture. An anilino/dimethylamino mixed-substituent polymer, [NgPiCtNHPh),-(NMeü)y(Cl)z]n (x = 1.50, y = 3.34, z = 0.16), and a 2,6-diphenylphenoxy/dimethylamino mixed-substituent polymer, [N3P2C(2,6-OPh(Ph)2)z(NMe2)>]" (x = 1, y = 4), were synthesized via the same technique. A mixedsubstituent polymer with regiospecifíc backbone carbon substitution, [(NP(OCH2CF3)2)2NC(N(Ph)2)]", was also synthesized. These mixed-substituent polymers are stable to water. The macromolecules were characterized by 31P, , and 13C NMR spectroscopy, IR spectroscopy, elemental analysis, differential scanning calorimetry, thermogravimetric analysis, and gel permeation chromatography. Poly [(dimethylamino)carbophosphazene] undergoes a depolymerization reaction in solution and in the solid state to give smallmolecule cyclic analogues, including NaPgCXNMe^s. The depolymerization reaction was investigated by 31P NMR spectroscopy and thermogravimetric analysis in conjunction with mass spectrometry. Analogous smallmolecule model reactions were undertaken in which the cyclocarbophosphazene NgPaCCU was allowed to react with primary and secondary alkylamines to yield the cyclic species NaPzCtNRiRa)* The mixed-substituent cyclic species {[NP(OCH2CF3)2]2[NC(N(Ph)2)]¡and {[NP(NMe2)2] [NP(2,6-OPh(Ph)2)(NMe2)] [NC(NMe2)]} were also synthesized.