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Conducting Copolymers of Thiophene-Functionalized Polystyrene

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Conducting Copolymers of Thiophene-Functionalized Polystyrene
   PLEASE SCROLL DOWN FOR ARTICLE This article was downloaded by: [TÜBİTAK EKUAL]  On: 5 June 2010  Access details: Access Details: [subscription number 772815469]  Publisher Taylor & Francis  Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK International Journal of Polymer Analysis and Characterization Publication details, including instructions for authors and subscription information: Conducting Copolymers of Thiophene Functionalized Polystyrene Özge Papila a ; Levent Toppare a ; Yusuf Yagci b ; Luminita Cianga ba  Middle East Technical University, Department of Chemistry, Ankara, Turkey b  Istanbul TechnicalUniversity, Department of Chemistry, Istanbul, Turkey To cite this Article  Papila, Özge , Toppare, Levent , Yagci, Yusuf and Cianga, Luminita(2004) 'Conducting Copolymers of Thiophene-Functionalized Polystyrene', International Journal of Polymer Analysis and Characterization, 9: 1, 13 — 28 To link to this Article: DOI: 10.1080/10236660490890411 URL: Full terms and conditions of use: article may be used for research, teaching and private study purposes. Any substantial orsystematic reproduction, re-distribution, re-selling, loan or sub-licensing, systematic supply ordistribution in any form to anyone is expressly forbidden.The publisher does not give any warranty express or implied or make any representation that the contentswill be complete or accurate or up to date. The accuracy of any instructions, formulae and drug dosesshould be independently verified with primary sources. The publisher shall not be liable for any loss,actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directlyor indirectly in connection with or arising out of the use of this material.  Conducting Copolymers of Thiophene-Functionalized Polystyrene O ¨zge Papila and Levent Toppare Department of Chemistry, Middle East TechnicalUniversity, Ankara, Turkey Yusuf Yagci and Luminita Cianga Department of Chemistry, Istanbul TechnicalUniversity, Istanbul, Turkey The syntheses of conducting copolymers of thiophene-functionalized  polystyrene and pyrrole (PS  = PPy) were achieved using p-toluene sulfonicacid (PTSA) as the supporting electrolyte via constant potential electro-lysis technique. Characterization of the samples was performed by acombination of techniques: cyclic voltammetry (CV), thermogravimetricanalysis (TGA), differential scanning calorimetry (DSC), scanning elec-tron microscopy (SEM), NMR, and FT-IR analyses. The conductivitieswere measured by the four-probe technique.Keywords : Conducting copolymers; Pyrrole INTRODUCTION The development of controlled radical polymerization in the scien-tific area opened the way to design many materials with new anddifferent potential applications that can be prepared only by thesemethods. The control of soft materials on the nanometer size scale isbecoming an increasingly important aspect of polymer science as moreresearch is directed toward the study of nanoscopic structures andmaterials. The preparation of well-defined nanostructures requires Address correspondence to Levent Toppare, Department of Chemistry, Middle EastTechnical University, Ankara 06531, Turkey. E-mail: International Journal of Polymer Anal. Charact. , 9: 13–28, 2004Copyright # Taylor & Francis Inc.ISSN: 1023-666X print DOI: 10.1080/10236660490890411 13  D o w nl o ad ed  B y : [ TÜ B T A K  E K U A L]  A t : 11 :47 5  J u n e 2010  molecular building blocks of well-defined structure; new syntheticmethods for introducing functional groups at specific loci at eitherchain ends or along the backbone are emerging as powerful tools forconstruction of these architectures [1] . Considerable effort has recentlybeen devoted to the development of viable ‘‘living’’ free radical pro-cedures for the synthesis of well-defined polymers with controlledincorporation of functional groups.The use of functionalized initiators yields polymer chains with a widevariety of functional groups using any of the three standard methods for‘‘living’’ free radical polymerization: nitroxide-mediated polymerization(NMP), atom transfer radical polymerization (ATRP), and radicaladdition fragmentation transfer polymerization (RAFT) [2] . Since themain advantage of the nitroxide-mediated system is the absence of anymetal, the goal of the present approach is to synthesize and characterize anew thiophene-containing stable nitroxide initiator and use it to obtain awell-defined functionalized polystyrene.Conducting polymers can be synthesized by either chemical orelectrochemical polymerization methods. Electropolymerization hasseveral advantages, such as simplicity, reproducibility, and thicknesscontrol [3–5] . Electrochemical initiation of polymerization reactions hasbeen applied to the synthesis of a wide range of polymer types [6–7] .However, some difficulties appear in processing conducting polymerssince they have poor mechanical and physical properties [8–11] . In orderto prepare useful materials from conducting polymers, there is a needfor good mechanical properties and environmental stability as well asconductivity. An obvious way to produce these polymers in a tough,processable, stable form is to make composites with stable, passivepolymers. In principle, this can be achieved by block or graft copo-lymerization, through synthesis of the conducting polymer within thehost, or by simple blending [12] . Alternatively, polymers with functionalgroups within or at the end of the chain can be used for the synthesis of copolymers.Polypyrrole is one of the well-known conjugated heterocyclicpolymers having high electrical conductivity and stability [13] . Theelectrochemical polymerization of pyrrole is usually done by electro-chemical oxidation of pyrrole on a Pt electrode that is already coatedwith insulating polymers [14–15] . The main purpose is to obtain homo-geneous composites that retain the characteristics of both polymers, atleast to a certain extent.In this study, thienyl containing TEMPO (2,2,6,6-tetra-methylpiperidinyl-1-oxy) initiated polystyrenes were synthesized. Mn:11.500 and 22.400 are denoted PS1 and PS2. Graft copolymers of thesefunctionalized polystyrenes and polypyrrole were synthesized by elec-trochemical methods.14  O ¨ . Papila et al.  D o w nl o ad ed  B y : [ TÜ B T A K  E K U A L]  A t : 11 :47 5  J u n e 2010  EXPERIMENTALMaterials 3-Thiophene acetic acid, 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl(4-hydroxy-TEMPO), benzoyl peroxide (BPO), and dichloro-methane(CH 2 Cl 2 ) (all Aldrich) were used without further purification. Thionylchloride (Fluka) and styrene (St) were distilled just before use, pyrrole (Py)wasdistilledbeforeuseandstoredat4  C,andp-toluenesulfonicacid(PTSA)was used as received. All solvents were purified and dried by standardtechniques before use. Preparation of the Intermediate and Initiator 3-Thiophene Acetic Acid Chloride The acid chloride of 3-thiophene acetic acid was prepared as pre-viously reported [16] .  1 H-NMR results are ( d , ppm from trimethyl silyl(TMS) in CDCl 3 ): 7.33–7.31, 7.24–7.16, 7.01–6.99 (2m, 1d, 3H fromthiophene ring); 4.16 (s, 2H,   CH 2 ). 4-Thienylacetyl-oxy-2,2,6,6-tetramethylpiperidinyl-1-oxy(thi-TEMPO) A solution of 6.98mmol of 3-thiophene acetic acid chloride in 2mLdry dichloromethane was added dropwise to a solution of 5.82mmol4-hydroxy-TEMPO (4-HTEMPO) in 10mL of dry dichloromethanecontaining 0.97mL triethylamine (TEA) (6.98 mmol), with stirring andunder cooling with ice. The esterification reaction was performedunder nitrogen atmosphere. The progress of the reaction was checkedby thin-layer chromatography. Upon completion of the reaction, thechloro hydrate of TEA was removed by filtration and the solution waswashed three times with acidified water (1%) and then with distilledwater (four times). The organic layer was dried on magnesium sulfateand then the solvent was removed by a rotaevaporator. Onto the crudethi-TEMPO methanol was added, and the black precipitated solid wasfiltered. The solution was evaporated and the pure product thi-TEMPO resulted as a brown-red syrup with 65% yield.Infra-red (IR) results ,cm  1 : 3100 (HC=CH in thiophene); 2990, 2900,2750 (CH 3  ,   CH 2  ,   CH  ); 1730, 1260, 1220 (ester); 1520, 760(thiophene ring); 1380 (TEMPO moiety).The representation of the synthesis of thi-TEMPO is presented inScheme 1. Conducting Copolymers  15  D o w nl o ad ed  B y : [ TÜ B T A K  E K U A L]  A t : 11 :47 5  J u n e 2010  General Procedure for the Synthesis of Thiophene-Functionalized Polystyrene Prepolymers The thienyl-containing polystyrene samples PS1 and PS2 were pre-pared in bulk and in solution respectively under stable free radicalpolymerization (SFRP) conditions using a bimolecular initiator systemconsisting of a mixture of BPO and thi-TEMPO. In both experiments apreheating at 95  C for 3.5h was performed to allow BPO to decom-pose completely. The polymerizations were conducted at 125  C for agiven time, shown as in Table I. Then the mixtures were cooled and theresulting products were purified by double precipitation in methanol.In the case of PS1 the reaction mixture was solidified. The reactionflask was cooled with liquid nitrogen, and the resultant material wasdissolved in dichloromethane and purified bythe above-mentionedprocedure. The reaction conditions and some characteristics of theresulting polymers are presented in Table I. SCHEME 1  Synthesis of the thi-TEMPO initiator. TABLE I  Preparation of thienyl-containing polystyrene by using thi-TEMPOSampleMolar ratio of components in thereaction mixture[M]:[BPO] : [thi-TEMPO]Reactionconditions  M  n,GPC  PD  M  n,NMRa PS1 200 : 1 : 1.32 bulk, 125  C,t ¼ 69h22416 1.6 NotdeterminedPS2 100 : 1 : 2 Xylene, 125  C,t ¼ 24h11513 1.35 11336 a Molecular weight calculated from the integrals ratio of the peaks in the1–2ppm range (attributed to three protons of styrene in the main chain) andthat of the peaks at 3.74ppm belonging to two protons in thiophene moiety. 16  O ¨ . Papila et al.  D o w nl o ad ed  B y : [ TÜ B T A K  E K U A L]  A t : 11 :47 5  J u n e 2010
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