Search

Using solid-state NMR methods the morphological behavior of poly[bis(trifluoroethoxy)phosphazene] was studied, employing four nuclei of interest – 1H, 19F, 31P and 13C. Measurements on all four nuclei support that at ambient temperature the crystalline and amorphous phases coexist. Variable temperature studies showed that above T(1) = 90° only a single highly mobile phase exists, which is presumed to be the 2D mesophase. All four nuclei showed that when heat cycling the polymer, repeatedly above T(1), an increase in crystallinity occurs with each cycle. For the first time 13C MAS NMR spectra, using high power 19F and 1H decoupling, were obtained, which exhibited the same behaviour domain. Filtered 13C{1H,19F} MAS spectra containing signal from the crystalline domain using the discrimination induced by variable amplitude minipulses (DIVAM) sequence were measured. Heat treated and solvent cast material showed differences in these 13C spectra, that were consistent with a decrease in backbone conformations upon heating, suggesting an increase in the extended chain form corresponding to the γ form. Analogous sensitivity to variations in crystal phase composition has not been seen previously using 1H, 19F and 31P methods, emphasizing the importance of 13C MAS methods to morphological studies of phosphazenes.

A modification of the method for synthesis of well-defined mono- and ditelechelic polyphosphazenes via the living, cationic polymerization of phosphoranimines has been developed. This process provides access to phosphazene block, comb, and graft copolymers that contain organic or organosilicon macromolecules. Several alkoxy and aryloxy phosphoranimines, RO(CF3CH2O)2PNSiMe3 (R = Ph, MeOPh, C10H7, BOC−NH−CH2CH2, t-BuMe2SiO(CH2)5, C8H11, and CH2CH−C6H4), were synthesized via the reaction between a bromophosphoranimine and the appropriate sodium alkoxide or aryl oxide. These species are potential initiators or terminators, useful for the synthesis of telechelic polyphosphazenes with etheric linkages rather than the amino linkages used previously. Ditelechelic polymers, RO[(CF3CH2O)2PN]n−P(OCH2CF3)3OR, were prepared by terminating living poly(dichlorophosphazene) chains, [Cl3PN−(Cl2PN)n−PCl3]+[PCl6]-, with these alkoxy or aryloxy phosphoranimines. Alternatively, monotelechelic polyphosphazenes were produced th...

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 Cl3PNSiMe3 and PhCl2PNSiMe3 are described. The ambient temperature polymerization of PhCl2PNSiMe3 is faster in toluene, benzene, and dioxane than in methylene chloride or chloroform. The polymerizations of Cl3PNSiMe3 and PhCl2PNSiMe3 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, RCl2PN−[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 ...

Nucleophilic aromatic substitution of cyclopentadienyliron complexes of chloroarenes with oxygen-containing nucleophiles led to the isolation of a number of aromatic ether complexes (2, 5a−e) in very good yields. Reactions of these complexes with 1-naphthol, followed by removal of the cyclopentadienyliron moieties produced aromatic ether compounds with terminal naphthoxy groups (3, 7a−e). Polymerization of these monomers in the presence of ferric chloride gave the poly(aryl ethers) 4 and 8a−e. These materials were obtained with weight-average molecular weights up to 139 900 g/mol. Thermogravimetric analysis of the poly(aryl ethers) showed that these materials displayed no significant weight loss until 458−575 °C. The glass transition temperatures for these polymers ranged from 147 to 226 °C, as measured by differential scanning calorimetry.

A new polyphosphazene, [N=PPh(CF 3 )] n , has been prepared via the PCl 5 -induced cationic polymerization of Me 3 SiN=P(CF 3 )(Ph)Br. In addition, the cationic route has been used to produce [N= PPh(Me)] n with controlled molecular weights and narrow polydispersities. By contrast, the new monomer Me 3 SiN=P(t-Bu)(Ph)F failed to polymerize under any conditions but was used as an initiator and terminator to prepare both mono- and ditelechelic polymers. This monomer was also used to prepare [F(Ph)(t-Bu)P=N(PCl 2 =N)P(t-Bu)(Ph)F] + , which was used as a substrate for reactions with alkoxy and aryloxy groups to yield the hydrolytically stable materials, [R(Ph)(t-Bu)P=N(PR 2 =N)P(t-Bu)(Ph)R 2 ].

A new approach to the design of monomeric and oligomeric ether and thioethers is presented in this article. Nucleophilic aromatic substitution (S N Ar) of cyclopentadienyliron complexes of chloroarenes with a number of aliphatic and aromatic dihydroxy or disulfide nucleophiles, led to the formation of the diiron complexes (2a-g) in very good yields. Some of these sulfur complexes were further oxidized to produce the sulfone complexes (4a-c). Functionalization of the diiron complexes with terminal chloro groups (2a, 2c and4a) was also achieved using S N Ar reactions. The cyclopentadienyliron moieties were removed easily by photolytic demetallation to give the free monomeric and oligomeric ether, thioether and sulfone compounds in yields ranging from 70 to 93%.

Synthetic strategies for the design of oligomeric ethers with pendant cyclopentadienyliron moieties have been developed. A wide range of these materials have been prepared via nucleophilic aromatic substitution reactions of a mono- or di-hydroxyaromatic nucleophiles and a variety of chloroarene complexes under mild experimental conditions. The mono- and bis-(cyclopentadienyliron) arene complexes were used as building blocks for the larger systems. The crystal structures of three bis(cyclopentadienyliron) arene dications, [(η5-C5H5)Fe(η6-C6H5)-o-XC6H4X-(η6-C6H5)Fe(η5-C5H5)]2+(X = O or S) and [(η5-C5H5)Fe(η6-C6H5)-m-OC6H4O-(η6-C6H5)Fe(η5-C5H5)]2+, have been determined by X-ray crystal structure analysis. A number of routes to the synthesis of the oligomeric species (tri-, tetra- and hexa-iron moieties) have been investigated to determine the flexibility and efficiency of the proposed strategies, and these materials have been fully characterized using spectroscopic and analytical techniques. To prove further the structures of these complexes, some of them have been prepared using different starting materials, giving the same proposed products. A series of polyiron complexes containing terminal hydroxy groups have also been prepared and used as dinucleophiles. The systematic increase in the number of rings and iron moieties allowed full characterization by monitoring the changes in the NMR spectra. Furthermore, the possibility of preparing homo- and mixed-polyaromatic ethers where the number of cyclopentadienyliron moieties varied from two to thirty-five has been demonstrated.