Synthesis and characterization of diethyl-p-vinylbenzyl phosphonate ...

Superficies y Vacío 22(3) 6-10,septiembre de 2009©Sociedad Mexicana de Ciencia y Tecnología de Superficies y Materiales136.35 ppm corresponding to the C atoms of the vinylgroup; the signals at 16.02 and 63.69 ppm due to the Catoms on the CH 3 and CH 2 of the diethyl-phosphonategroup, respectively.Formation of the DEpVBP is also evident from their FTIRand Raman spectra (see Fig. 3 and Fig. 4). IR spectrumrevealed strong absorption bands due to the P=O stretchingvibration mode at 1266 cm -1 , P-O-Et stretching at 1099-1020 cm -1 , P-O-C stretching at 989 cm -1 , all correspondingto the –PO(CH 2 CH 3 ) group; C=C stretching vibration modeat 1630 cm -1 of vinyl group; and C=C stretching at 1608cm -1 of phenyl group. These assignments were based onliterature vibrational studies of organic and phosphonatematerials [14-17]. On the other side, in the Ramanspectrum the signals corresponding to the C=C stretchingmodes of the vinyl and phenyl groups appeared at 1630 cm -1 and 1607 cm -1 , respectively.3.2. Polymer characterizationThe poly(DEpVBP) homopolymer was found to besoluble in several polar solvents like ethanol, methanol,DMF, and DMSO; but insoluble in toluene, ciclohexane,and water. Formation of the homopolymer was followed byRaman and IR spectroscopies. Fig. 3 and Fig. 4 show theIR (4000-400 cm -1 ) and Raman (in the spectral range of3500-500 cm -1 ) of the monomer and polymer, indicatingthe region correspond to the C=C stretch. Is clear fromRaman spectra that the principal evidence of polymerformation came from the disappearance of the signal due toC=C stretching vibration mode of vinyl group of themonomer. In the IR spectrum of the polymer (Figure 3)also the absorption band due to C=C stretching of the vinylgroup is absent.Thermal stability of the poly(DEpVBP) was studiedthrough thermogravimetric measurements realized at aheating rate of 10°C/min under nitrogen atmosphere.Figure 5 Termogravimetric curve of the polymer showsdistinct regions of weight loss with the increase oftemperature. The first, a gradual weight loss of about 3.4 %in the temperature range 120-208 °C was attributed to theevaporation of water and DMF. In the second region (208-305 °C), about 13.2 % of the weight loss was associated tothe partial thermal degradation of poly(DEpVBP) due tothe loss of the ethyl ester group of the vinylbenzylphosphate. Thermal degradation of VBP due to the loss ofester groups has been reported at 240-250 °C [13].Progressive thermal degradation of the polymer observedbetween 305 and 500 °C, is probably due to thedegradation of the main chain of polymer and thedegradation of P-C bonds of the pendant group of polymer.These results indicate that the poly(DEpVBP) synthesizedis stable until 208 °C. Above this temperature, thedegradation of polymer occurs in several steps, resulting inthe loss of about 47 % of the weight of polymer.4. ConclusionsDEpVBP monomer was synthesized by means ofMichaelis-Arbusov reaction using CuCl 2 as inhibitor agentand chlorebenzene as solvent, with a yield of 75%.Synthesis process permits to improve the yield on reported(68%). Poly(DEpVBP) synthesized by free radicalspolymerization shows a good thermal stability until 208 ºC.Molecular structures of the synthesized compounds wereconfirmed by 1 H NMR, 13 C APT NMR, IR, and Ramanspectroscopies. Owing to the ion exchange capacityconferred by the phosphonate group and the good thermalTable 1. Assignment of 1 H-NMR peak positions of the DEpVBP monomer.Chemical Shiftδ (ppm)Integration MultiplicityJ H-H(Hz)AssignmentH 7'H CH1.82 2 s --- H 3 1 C H 2 CH 2 21.33 6 t 6.96 H 1 27.39 2 d 8.04 H 55 H7.33 2 d 8.2 H 46.70 1 m --- H 64 H5.76 1 d 7.57 H 7O5.27 1 d 10.98 H 7’P4.11 4 m --- H 2OH 3 C O7CCH 236CH 31H 5H 4s = singlet, d = doublet, t = triplet and m = multiplet9