Ferda Hacıvelioğlu

Azole substituted polyphosphazenes as nonhumidified proton conducting membranes

Novel nonhumidified proton conducting membranes have been prepared from the reactions of triazole (Tri) and aminotriazole (Atri) compounds with poly[(4-methylphenoxy)chlorophosphazene] (PMPCP). The composition of the novel polymers (TriP and AtriP) was verified by elemental analysis (EA) and the structure was characterized by FT-IR, 1H and 31P NMR. Size exclusion chromatography was used to confirm the polymer formation. Thermogravimetric analysis (TGA) showed that the samples are thermally stable up to approximately 150 °C. Differential scanning calorimetry (DSC) results illustrated the homogeneity of the materials. To obtain sufficient proton conductivity at high temperatures in the anhydrous state, the polymers were doped with trifluoromethanesulfonic acid (TA) at various molar ratios, x = 0.5, 1, 2 and 3 with respect to the azole unit. The proton conductivity of the polymer electrolytes was measured using high resolution dielectric-impedance analyzer. The proton conductivity of these materials increased with dopant concentration and temperature. Maximum proton conductivity of TriP2TA and AtriP2TA were obtained as 3 × 10−3 S cm−1 at 50 °C and 0.0412 S cm−1 at 130 °C respectively, in the anhydrous state.

Dimorphism in 4,4,6,6-tetrachloro-2,2-(2,2-dimethylpropane-1,3-dioxy)cyclotriphosphazene and 6,6-dichloro-2,2:4,4-bis(2,2-dimethylpropane-1,3-dioxy)cyclotriphosphazene.

A second, polymorphic, form of the previously reported compound 4,4,6,6-tetrachloro-2,2-(2,2-dimethylpropane-1,3-dioxy)cyclotriphosphazene, C(5)H(10)Cl(4)N(3)O(2)P(3), is now reported. The molecular structures of these two compounds are similar, aside from minor conformational differences. However, the compounds crystallize in two different space groups and exhibit quite different crystal structure assemblies. Additionally, 6,6-dichloro-2,2:4,4-bis(2,2-dimethylpropane-1,3-dioxy)cyclotriphosphazene, C(10)H(20)Cl(2)N(3)O(4)P(3), is shown to exhibit two different conformational polymorphs when crystallized from different solvent mixtures. The alpha form crystallizes in the space group Pnma with the molecular structure lying on a mirror plane (symmetry code: x, -y + {1/2}, z), whilst the beta form is in the space group C2/c with the molecular structure lying on a twofold axis (symmetry code: -x, y, -z + {3/2}). The difference between the two molecular structures is in the conformation of the spiro-ring substituents with respect to the phosphazene ring. The resulting crystal structures give rise to differing packing motifs.

Preparation of sulfonic acid functional proton conducting phosphazenes by covalent protection

An easy and efficient method has been developed to prepare sulfonic acid functional cyclic and polymeric phosphazenes. Hexa(ethyl 4-oxybenzenesulfonate)cyclotriphosphazene and its sulfonic acid derivative, hexa(4-oxybenzenesulfonic acid)cyclotriphosphazene were successfully synthesized. Fully sulfonated polybis(4-oxybenzenesulfonic acid)phosphazene and three different copolymers composed of 4-methylphenol and 4-hydroxybenzenesulfonic acid have been prepared, in which the degree of sulfonation for whole polymers ranged from 25% to 100%. 1H, 31P NMR and FT-IR techniques were used to characterise the composition of the materials obtained by this new synthetic route. The structure of the hexa(ethyl 4-oxybenzenesulfonate)cyclotriphosphazene was also determined by single crystal X-ray diffraction. The thermal properties of the materials have been investigated by DSC and TGA, and the ion exchange properties were measured using volumetric titrations. The mechanical properties of the cast membranes were measured by using a universal tensile apparatus and compared with Nafion and post sulfonated aryloxyphosphazenes. Impedance spectroscopy was used to investigate the proton conductivity properties of the phenoxysulfonic acid substituted cyclic and polymeric phosphazenes at various temperatures. It was found that the proton conductivity of fully sulfonic acid functional polyaryloxyphosphazene is higher than that of Nafion under anhydrous conditions. Due to the advantages of this new synthetic route over the previous methods, it will be possible to prepare novel sulfonated phosphazene derivatives for different applications.

The reaction of hexachlorocyclotriphosphazatriene with bromoneopentyl glycol

- In the present work, novel phosphazene derivatives, monospiro- (1), dispiro- (2), and trispiro-2,2-bis(bromomethyl)-1,3-propandioxy (3) substituted cyclotriphosphazatrienes were synthesized with the reaction of bromoneopentyl glycol(2,2-bis(bromomethyl)-1,3 -propandiol) with hexachlorocyclotriphosphazatriene, N 3 P 3 Cl 6 . The structures of the compounds were determined by elemental analysis, mass spectrometry, 1 H and 31 P NMR spectroscopy. The thermal properties of the compounds (1), (2) and (3) were investigated by DSC and TGA.

A novel water-soluble and self-doped conducting hybrid copolymer: poly(4-oxybenzenesulfonic acid)phosphazene-g-poly(3,4-ethylenedioxythiophene)

A different approach is clearly necessary to overcome the solubility problem of poly(3,4-ethylenedioxythiophene). Here, a synthetic strategy was followed to synthesize PEDOT graft arms on a polyaryloxyphosphazene platform, which is also carrying sulfonic acid co-substituents. It is found that the conductivity of the novel copolymers increases with an increase in the PEDOT level.