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These salts can be removed by using an aqueous extraction phase. The slurry causes poor mixing, which leads to poor heat transfer, i. The mentioned problems significantly lower the yield and capacity of the process. In order to provide a minimum of mixing and heat transfer of the exothermal reaction usually a solvent has to be added 1,3-dioxolane. The products can be easily recovered by a simple layer separation, where the upper phase mainly contains the polymer product and the lower layer mostly consists of 1-methylimidazolium chloride ionic liquid , which could be converted to 1-methylimidazole by treating with NaOH aqueous solution at a room temperature.

The inherent viscosities of all polymers were in the range 0. The yield of the process decreases in the case of TEA and results indicate that the polycondensation system requires 1-methylimidazole as acid scavenger instead of TEA. Polymeric structure was supported by P-O-C aliph peaks at — cm -1 and cm -1 , respectively.

The disappearance of the phosphonate P-OH stretching band at — cm -1 indicates that the polymer is indeed a polyphosphonate. The resonance of the phenyl group falls in the range 7. The presence of phosphorus is confirmed by elemental analysis and 31 P-NMR spectrum.

The 31 P-NMR spectra of all polymers present two signals: one corresponds to the P in the repeat unit and other one to the P at the end chain, and confirm successful incorporation of phosphorus in the polymer backbone [ 36 , 37 ]. This process corresponds to the cleavage of PEG backbone. These temperatures are higher in the case of polymers P2 and P4 than for P1 and respectively P3. An increase of EG units in polyphosphonate improves polymer thermal stability. A melting process was observed on DSC curves for all samples.

Also, it was noticed that using TEA as acid scavenger the polymers are obtained with an increase polydispersity, most likely due to the low heat transfer during polycondensation.

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Synthesized compounds were tested as flame retardants using LOI method. These polymers show LOI values in the range 26—29, comparable with other polyphosphonates and polyphosphates [ 38 ]. Based on the polymer P3 and P4 obtained by method b with MeI as acid scavenger, different membranes with variable lithium salts contents were prepared. These interesting tendencies in physical properties of the membranes are the consequence of the decrease in flexibility of chains due to an increase in intramolecular and intermolecular coordination between active sites of the polymer chains.

The complexation of polymers with lithium salts allowed the ions to act as transitory cross links [ 39 ]. Also, the surface of the membrane containing high salt concentration is less smooth compared with the low and middle salt concentration membranes. The thermal stability of the membranes based on the polymers P3 and P4, flame retardancy, conductivity and ion transference number were investigated.

Phosphorus-Based Polymers: From Synthesis to Applications

The complexation of polymers with lithium salt affects the melting temperature, Tm, of the membrane. This behavior is attributed to the process of the inhibition of crystallization by the presence of the salt practically a reduction in crystalline fraction.

Even at lower salt concentration a decrease of Tm takes place due to the intercalation of lithium ions and decrease in polymer—polymer interaction. The presence of the phosphonate group reduces flammability both of the parent polymers and membranes based on them. In order to evaluate if the polymers P3 and P4 can be used as polymer electrolyte for SPE, the ionic conductivity at different temperatures and ion transference number were determined. The difference between the membranes lies in the structure of polymer P3 or P4 and in the salt content. The data indicate that the polymer with a greater amount of EG unit P4 facilitates the ion transport showing higher ionic conductivity.

At the same salt content, the highest conductivity was obtained for membrane based on P4. The decrease of conductivity was attributed to the decrease of the available number of charge carriers due to ion aggregation. This value is higher than the conductivity observed for pure PEG , of 1. The conductivity of all membranes increases with the increase of the temperature. This tendency leads to the increase of ions and chains mobility.

The polymer can expand easily when the temperature increases, the free volume increase and polymer segments can be without difficulty in motion. Practically, these enhance in mobility can compensate the retarding effect of the ion clouds. The variation of the conductivity vs. The evolution of conductivity as a function of the temperature for membranes based on P3.


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The evolution of conductivity as a function of the temperature for membranes based on P4. The activation energy Ea values were calculated from the linear segment of all plots using the equation 1 :. The activation energy, Ea can be calculated from the slope and the pre-exponential factor can be obtained from the intercept with the vertical axis. The conductivity plotted in Arrhenius coordinates for membranes based on P3. The conductivity plotted in Arrhenius coordinates for membranes based on P4.

The regression values R are close to unity and, therefore, the dependence of ionic conductivity on temperature, for all the complexes, obeys Arrhenius law R 2 lies between 0. The conductivity of polymer electrolytes is affected by the number of charge carriers and their mobility [ 40 ]. The low activation energy values were obtained for membranes with higher amount of EG unit P4. The low activation energy value obtained for P4 membranes indicates that the ion transport is possible by the lower energy barrier to the ions transport in this copolymer matrix.

The structure of the P4 polymer is capable to reduce the apparent activation energy for ion transport and also to increase the local free volume of the matrix. The activation energy depends on salt content which is the source of charge carriers in the polymer electrolyte the decrease activation energy is due to the increase number of charge carriers in the polymer electrolyte. This is a consequence of two factors: the first is the number of charge carriers and second is the tendency to aggregate.

Practically, the increase in number of charge carriers with the increase of salt content can be overcome by the effect of the ion clouds. At high salt concentration in membrane the salt exists as ion pairs or aggregated ions that could slow down ion transport resulting in a decrease of conductivity.

The highest values explain the increase of conductivity in this polymer as a result of the higher quantity of mobile charge carriers in the membranes. A greater amount of EG unit in the P4 matrix shows an improvement of polymer complexation.

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Similar observations are also reported by Jeon et al. The total ionic transference number was found to be in the range of 0. Also, the total ionic transference number is higher for membranes based on P4 and confirms the observation regarding the improvement of salt complexation due to the greater amount of EG unit in the P4. The elasticity tests were performed by measurement the shear stress, and the elasticity modulus. Higher conductivity and good thermal stability of this membrane could be attributed to the optimum composition, with a good balance between EG unit and salt content.

Reagents 4-chlorophenyldichlorophosphonate CPPD and poly ethylene glycol and from Aldrich, were used as received. Methanol without purification, Aldrich and ethylene carbonate EC, without purification, Aldrich were used for membrane formation. After the reaction was completed, HCl.

TEA side product was filtered 4—5 times. The 1,3-dioxolane was removed by the vacuum evaporation on a rotary evaporator. The products P1 and P2 were white solids. P2: IR KBr, cm -1 : After the reaction is completed two clear liquid phases occurred that can be easily separated. The upper phase is the polymer solution and the lower phase is the pure ionic liquid.

The ionic liquid formed in the lower layer was separated, and then washed with sodium hydroxide to recycle the 1-methylimidazole. The 1,3-dioxolane solution was removed by vacuum evaporation on a rotary evaporator. The products P3 and P4 were white solids. P4: IR KBr, cm -1 : Polymer electrolytes membranes were prepared based on P3 and P4 polymers obtained with MeI as acid scavenger.

Certain amount of lithium salts i. The elasticity tests were performed using Anton Paar Rheometer. Ionic conductivity of the membranes was determined by the AC impedance spectroscopy. The impedance tests were carried out in the frequency range from 0. The sinusoidal potential amplitude was 10 mV.

All electrochemical measurements were performed at room temperature ambient condition.

Phosphorus-Based Polymers - From Synthesis to Applications - Knovel

For each spectrum 60 points were collected, with a logarithmic distribution of 10 points per decade. The sample films were sandwiched between symmetrical cells containing blocking stainless steel SS electrodes. Analysis of the impedance spectra is based on the Bode diagrams. In this case, the overall impedance and the phase shift between applied voltage and answering current signal are both plotted against the frequency. At the point where the phase angle is zero or close to zero , the impedance is pure ohmic and the resistance of the membrane can directly be determined and used for the ionic conductivity calculation, by the following equation 2 :.

The total ionic transference number was calculated from plots of the polarization current versus time with the equation 3 :.

Biomedical applications of phosphorus-containing polymers

Where I i is the initial current and I f is the final residual current. In order to reduce the risk of fire in lithium-ion battery new polymers containing phosphorus groups and polyethers were developed. Polymers composed of phosphonate as a linking agent and poly ethylene glycol s were synthesized in order to increase local segmental motion and improve ion transport.

Polymer electrolytes were synthesized by solution polycondensation of 4-chlorophenyldichlorophosphonate as a linking agent and PEG with different molecular weights MW of and The advantages are: an ionic liquid is formed and the products can be easily recovered by a simple layer separation; the enhancing of polymer yield; reducing of the corrosion problem. The temperature - conductivity dependence of the copolymer exhibits Arrhenius behavior and the activation energy increases by increasing the content of EG unit.

This decrease in conductivity at higher salt concentration is due to the ion aggregation.


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