new polym mat 3(3) 155-161 1992 lárez márquez perdomo márquez

8/3/2019 New Polym Mat 3(3) 155-161 1992 Lrez Mrquez Perdomo Mrquez

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New Polymer icMoter . , VoI . 3 , No . 3, pp . 155-161 1992)!6) VSP 1992.

Electrochemicalpolymerization of p-2-furylacrylic acidCRISTBAL REZ, JAIROMRQUEZ,*GILBERTOPERDOMOandOLGA P. MRQUEZDrpor,rrrnt of Chemistry, F'aculty of Science,Universictad de Los Andes, Mrida 5101, Venezuela. \e . " r cd ' l J F cb ru a ry1 9 9 2Abstract-An electrochemical study of /-2-furylacryl ic acid in acetonitr i le/tetrabutylammoniumtetrafluoroborate on a platinum electrode, with in the potentia l range +2.000 to 2.000V versusAg,zAg*, showsoxidation (+ 1.800V) and reduction - 1.100V) peaks.An oligomer of molecularweight(M,,)2670 s produced,wi th 90o/o onversion,when anodicpulsedpotentiostatic lectrolysiss performcdusing a monomer concentr ationhigher than l0mM. The ol igomerization s believed o occur throughfuranic-furanic double bond interaction,according o the spectroscopic nalysis.Key word.s: rurylacryl ic ci d electro-oxidation, l igomerization,polymerization,and electrolysis.I. INTROI)UCTIONPhotodimerization an d photopolymerization of trans-p-2-furylacrylic cid (FAA)havebeen eported o occur n the crystall ine tate ] . Th e solid-state hotoreactionmechanism ha s additionally been consideredby Ghosh and Misra [2] using lR,Raman, electronicand laserRaman phonon spectroscopicechniques.There s no writtenevidence f theelectrochemistry f FAA in solution. Very itt leinformation is availableabout theeffect of the reactionvariables n the polymeriza-tion mechanism r about the distribution of productsan d their optical, hermal, andmechanicalproperties.The rapid developmentof organic conductivepolymers ik epolypyrrole, polythiophene,an d polyfuran ha s encouraged he study of its deriva-ives an d related compounds. An example s th e preparation of transit ion metal

by Sarawastiand Kapoor [3] .In this paper, we report th e resultsof an anodic study of FA A in non-aqueousmedium and discuss he effect of various electrolysisparameterson the electro-chemical eaction.Th e aim of this work was to seekconditions or the polymeriza-tion and to learn more about the propertiesof the polymer produced.2. EXPERIMENTAI,2. I . ChemicslsFuryl acrylic acid wa s synthesized4], recrystall izedro m benzene, nd then treatedwith activecarbon. lts meltingpoint and neutralizationequivalentwere 143'C an dI 39 g/equiv., respectively.

ET o whom correspondence hould be addressed t Apartado postal 459, Mrida 5101,Venezuela rUniversidad de Lo s Andes, Facultad de Ciencias, Departamento de Quimica, Laboratorio de Electro-qumica, edif. A La Hechicera,Mrida 5101, Venezuela.


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15 6 C. Lrez eI al.Th e supporting electrolyte, etrabutylammonium tetrafluoroborate (TBATFB)wa s preparedby a modified Fleishmanmethod [5]. Acetonitri le (HPLC grade)wa skept dry on 4, 4 molecular sieve.Al l chemicalswere highly pure. Th e experimentswere un underan argonatmosphere.

2.2. Cells and electrodesA typical one-compartment oltammetric cell wa s used.The working electrodewa sa 0.15cm2 platinum disk facing a platinum ring as the counter-electrode. repara-tive coulommetry was performed in a three-compartmentcell with two 15cm 2(geometric rea)platinum gauzes s working an d secondary lectrodes. l l measure-ments were aken againsta AglAgNO, reference lectrode.2.3. InstrumentqtionVoltammetric experimentswere un in a BAS l00A electrochemical nalyser.Pulsedand constant potential electrolyseswere performed with a PAR 173 potentiostatcoupled o a PAR 175 universalprogrammer.IR spectrawere aken using Acculab 2 Beckmanand Perkin Elmer 1725XFTIRspectrometer. he NMR an d UV spectrawere recordedusing A-60 Varian and 634Varian spectrometers, espectively.Cel permeation chromatograms (GPCs) weremonitored by an ALC-GPC-2O1 high performance iquid chromatograph with aPS-20Lichrogel column.3, Rts,SULTS3.1. Cyclic voltammetryIn acetonitri le/TBATFB, FA A presentsan oxidation peak at +1.800V and acounterpart educt ionpeak at -1.100 V (Fig. l ) .This study was devoted o the oxidation process.As the potential sweep ate (v )is changed,a singlediffusion-controlledelectron ransfer s observedwithin 0.1 an d0.6Vs-t (F ig. 2) . F igure3 shows he ef fect of changing he concent rat ion f the

2.5 0 '0 - 'uE V - tI' igure l. Cyclic voltammogram of FAA in TBATFB,zCH.CN. (a ) Electrolytic medium; (b ) I mM FAA.v : l0 0 mV s - r .


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6 . 0

Electropolymerization of furylacrylic acid

1t l z _ t l L t l z] X M V S

* * 4 . 0E

r < 2 n-( )

0 . 0200 - t] r m V * s

Figure 2. Effcct of the potentia l sweep ate on the peak current..-Cr,AAmM ) : ( l) 3.3; (+) 6.6; (O) 9.9;( ! ) 1 3 .2 ; x ) 1 6 .4 ; O)2 a .a ; ( A) 3 2 .3 . a ) 1 nvs . v ' " ; (b ) I , / v t /2 vs . v .

0 1 . 0 2 0 3 . 0- lC x m MF ig u re 3 . E f fe c to f th e co n ce n t ra t io n o f A A o n th e p e a kcu r re n t . v (mvs ' ) - ( r )5 0 ; (+ )1 0 0 ; (o )1 5 0 ;( ) 200; (x ) 300; (O ) 400; ( ) 500; (a ) 600.

40 0


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15 8 C. Ltirez et al.monomer, CM. At low valuesof CM, the behaviour s that of a pure diffusionalprocess.However, an increase f cr leads o a complexprocess, nd a shif t of thepeak potential(Ep) owards more posit ivevalues,with an increase f the sweep ate,is observed rom the voltammosrams.

0 400 800, - lt xm tn

1200l i g u re 4 . Cu r re n tva r ia t io n w i th t ime l ' o rF A A co n s ta n tp o te n t ia l l e c t ro l yse s .- -lyt ic medium; (O) 22 mM ; (O) 0. 5 mM .

F

Fx

4000 2000 1500JXcm

1000 500Figure 5. IR spectra. (a ) FAA; (b ) FAA electrolysisproduct.

t -3tx

1 .U0 0 . ( r ) E le c t ro -

/ 060504 0

3000

( a )


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Electropolymerization of furylacrylic acid3.2. CoulommetryPreliminary controlled-potentialelectrolyses arried out at +1.800V allowed us tooptimize the condit ions for further experiments.At CM valuesbelow l0-a M, thereaction reached completion; while at higher concentrations, a rapid fall in theelectrolysiscurrent wa s observed (Fig. 4). Pulsed potential electrolysisswitchedf rom 0.000V to +1.800V dur ing 55 s wi th a delayof 5 s, carr iedout for 50h on a5 x 10-2M FAA solution yielded9090 of polymerization.3.3. AnalysisThe hard, shiny,black main product shows, n its IR spect rum Fig. 5b), a remark-able reduction n magnitude of the C:C stretchingsignal at l650cm-r comparedwith the starting material (Fig. 5a), revealinga reductio n in the total number ofdouble bonds. The 'H-NMR spectrum Fig. 6) showsa ne w signalatd : 5 pp m which corresponds o th e protons of t he methyl groups formed from the

6 .0PPM/ )

l ' igure 6. 'H-NMR spectra. (a ) FAA; (b ) FAA electrolysisproduct.

15 9

( a )


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160 C. Lcirez et al.

) xrnl - igure 7. UV spectraof FA A ( - ) an d FA A electrolysis roduct (-) .addition reaction.Comparison of the UV spectra n Fig. 7 shows hat the monomerproducesa signalwith ,.-o* : 290 nm which shifts owards 312nm after thereactionis completed. Gel permeation chromatography of a 6090 w/w fraction of theproduct soluble n THF (Fig. 8) givesM" : 2670,M* : 6480,and D : 2.42 for theproduct, suggestinghat an oligomer mixture is obviouslypresent.

200 240 280, _ lC r X S

I' igure 8. Ge l permeation chromatogram for the FAA electrolysisproduct.4. DISCUSSIONFuryl acrylic acid is a good candidate for either oxidization or reduction underchosen conditions. The electrochemicalechnique appears o be eff icient for thepolymerization of FA A with a high conversionpercentage, nvolving a markedinfluence of the monomer concentration rom a Dure diffusional mass ransfer at

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Ocl

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Electropolymerization of furylacrylic acidlo w concentrationso a more complexcontrol process t concentrations igher han10mM. Above this limit value of C4, z complete eaction by controlled potentialcoulommetry was not achieved. nterruption of the appliedpotential restores hecurrent value when the electrolysiss switched over again. This sort of blocking-deblocking of the electrodesurfacesuggestshe convenience f a pulsedpotentialexperimentperformance 6] . Pulsedelectrolysis f the systemallows he formationof the product in an amount equivalent to 9090 of the starting material. Sixty percent (w/w) of the main product was soluble n THF. This fraction was analysedspectroscopically.Undoubtedly, the oligomerizationoccurs through the carbon-carbondoublebond since he IR s ignalat 1650cm-td imin ishesand a new NMRsignalat d:5.0ppm appears. rom the IR spect rum t can be assumed hat theether signal remains 11200cm-') and the furanic ring is kept. The depressionrbserved n the signal s attributable o double-bond oss.With these esultswe are sti l l unable to discriminatebetweenolefinic-olefinic,furanic-furanic, an d furanic-olefinic bonds for th e process of addit ion of themonomer. I t seemsmore feasible hat a mixture of them is occurring. Nevertheless,ou r data suggest furanic-furanic interaction according o the schemebelow:

l_p_c *l o l I I\ t :cHl,ICHCHloot

which agreeswith the appearance f the ne w NM R signal and the shift in the UVspectrum.An oligomer s believed o be the main reactionproduct with an averageof l9 units in the chain.Acknowledgements'V e would like to thank CDCHT-ULA and CONICIT for f inancial support.R[,I.-ERENCESl. M. Lahav and G. M. J. Schmidt, J. Chem. Soc. B 239 (1967).2. U. Ghosh an d T. N. Misra, - / . Polym. Sci.Polym. Chem. Cd. 26, 168l (1988).3. R. Sarawasti nd P. Kapoor, Transil ion. Met. Chem- 9' 35 (1984).4. A. l. Vogel, zl Texlbook of Practical Orgonic Chemistry. Longmans, London (1970).5. M. Fleishmanan d D. Pletcher, Tetrcthedron ett.60,6255 (1968).6 . O . P . M rq u e z ,Re v . Ro u m. Ch im.3 l ,7 1 1 (1 9 8 6 ) .

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new polym mat 3(3) 155-161 1992 lárez márquez perdomo márquez

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