红外光谱研究聚吡咯沉积在掺杂羊毛的相互作用_图文

1、Fibers and Polymers 2006, Vol.7, No.2, 105-111FT-IR Study of Dopant-wool Interactions During PPy DepositionAlessio Varesano, Annalisa Aluigi, Claudio Tonin*, and Franco Ferrero11CNR-ISMAC, Institute for Macromolecular Studies, C.so G. Pella, 16 13900 Biella, ItalyPolitecnico di Torino, Dip. Scienza

2、dei Materiali e Ing. Chimica, C.so Duca degli Abruzzi, 24 10129 Torino, Italy(Received January 20, 2006; Revised March 8, 2006; Accepted April 7, 2006Abstract: Coating the fibre surface by in situ oxidative chemical polymerisation of polypyrrole (using FeCl3 as oxidant is areadily industrial applica

3、ble way to give electrical properties to wool with good ageing stability 1, although pre-treatmentsare required to avoid damage of the cuticle surface due to the acidic condition of the process. FT-IR and EDX analysis revealthat organic sulphonates and sulphates, used as dopants, are absorbed by woo

4、l, while chlorine ions are preferably embeddedon the polypyrrole layer. The resulting electrical conductivity seems mainly due to the presence of chlorine as counter-ion ofpolypyrrole; nevertheless, the presence of arylsulphonate in the polymerisation bath increases the electrical conductivity ofthe

5、 coating layer.Keywords: Polypyrrole, Conducting polymer, Dopant, Wool, TextileIntroductionTextile materials generally show poor electrical conductivity.Several methods have been developed to improve the electricalproperties of synthetic fibres, but few of them are suitable fornatural fibres, partic

6、ularly for wool. Coating the fibre surfacewith a thin film of conducting polymers (i.e. -conjugated polymers as polypyrrole and polyaniline by in situ chemicaloxidative polymerisation in the presence of organic dopants, isthe most promising way to improve the electrical performancesof natural fibre

7、based textiles, since conducting polymers have already demonstrate good affinity to protein and cellulosefibres 1-3.Doped -conjugated polymers produced by oxidative polymerisation, contain positive charges on the backbone chain. It is supposed that the charged species are polarons(charge +e, spin 1/

8、2 and bipolarons (+2e, 0, which are delocalized over portion of several monomer units. The mobilityof charged species along the polymer chain is responsible forthe electrical conduction. The charges are neutralized throughthe introduction in the polymer structure of negative chargedcounter-ions. The

9、 counter-ions (also called dopants play animportant role in the synthesis of conducting polymers, becausethey promote the stability of polarons and bipolarons producingcomplexes 4,5.In the case of polypyrrole (PPy, positive charges are formedin the backbone chain during the chemical oxidative polyme

10、r-isation. A wide range of counter-ions can be incorporated intoPPy; they are generally organic sulphonates or sulphates 6-9or inorganic ions such as ClO 4, Cl , NO 3, SO 42 9-11.The type of counter-ion greatly influences the properties (e.g. morphology, structure, conductivity and stability of thew

11、hole polymer 9,12-14.On the other hand, it is well known that anionic surfactants,in particular alkylsulphates or arylsulphonates, are absorbed*Corresponding author: c.toninr.it105by wool 15-17 and a recent work 18 has disclosed thatsodium dodecylsulphate, absorbed onto wool surface, formsbilateral

12、micelles. Moreover, it was demonstrated that anionicsurfactants in acidic condition, greatly increase the acid damage of wool 15.In a previous work 19, differences in electrical conductivitywere obtained for PPy coating on different kinds of wool subjected to usual industrial treatments. In particul

13、ar, the electrical conductivity was found to decrease following theseries: Hercosett ® wool > Basolan ® wool > raw wool >Mohair fibres.Knitted fabrics were already industrially produced from conductive wool fibres treated with PPy. The fabrics showedgood properties, satisfactory p

14、erformances and stability to use 1. Moreover, it seemed that some interactions betweenfibres and dopant took place during the PPy deposition processes, although an exhaustive study on the interactionsbetween the reagents (oxidant, dopant, monomer and the substrate was not yet carried out, in spite o

15、f those influencethe deposition process and the final result.ExperimentalMaterialsThe chemicals used were Pyrrole, 97% (Py, Fluka as monomer; Iron (III Chloride Hexahydrate, 98% (FeCl3, Fluka and Ammonium Persulfate, 98+% (APS, Aldrich asoxidants; Naphthalenedisulfonic acid, disodium salt, 97%(NDS,

16、Aldrich, Naphthalenesulfonic acid, sodium salt, 90%(NS, Aldrich, Dodecylsulfate, sodium salt, 98% (DS, Aldrichand Dodecylbenzenesulfonic acid, sodium salt, tech. (DBS,Aldrich as dopants. Other chemicals were Hydrochloric Acid 0.5M (HCl, Riedel-de Haën for pH correction and Nonylphenol-20-Ethyle

17、nglycol Ether (NPE, Ilario OrmezzanoSAI as non-ionic surfactant to facilitate the impregnation ofwool.Loose fibres were Hercosett ® merino wool (18.6µm,106Fibers and Polymers 2006, Vol.7, No.2Alessio Varesano et al.Basolan ® merino wool (21µm, raw merino wool (19.5 µm and Mo

18、hair fibres (30 µm supplied by Filatura di TriveroS.p.A. (Gaglianico, Italy. Hercosett® and Basolan® processesare frequently used to provide felt-proofing and shrink-resistance to wool. The Hercosett ® process consists of an acid chlorination step followed by the application of a

19、 polymer thin film (e.g. cationic cross-linking polyamide-epichlorhydrin polymer on the fibre surface, in order to envelop the external scales of the cuticle cells and preventfibres motion with differential friction in the tip-root direction, which is recognised to be responsible for shrinkingand fe

20、lting 16,20-23. The chlorination results in the oxidationof cystine residues into cysteic acid residues on the surfaceof the wool fibres and allows the cationic polymer to spreadand adhere to the wool surface 22,23. The Basolan® processconsists of a chlorination step (e.g. dichloroisocyanurate

21、saltfollowed by neutralisation and dechlorination; resistance toshrink and felt is mainly due to the oxidative corrosion of thesurface scale-shaped cuticle cells 21,24. The fibres were used as received because already scoured and no additiveswere present.MethodsA first series of samples was treated

22、with dopants (NDS,NS, DS or DBS and oxidants (FeCl3 or APS or pH corrector(HCl with the aim of evidencing the interaction between thereagents and the fibres. The concentrations of the solutionswere 0.105 N of oxidant or HCl, 0.0175 M of dopant. Thetreatments were carried out at room temperature in t

23、he presence of the non-ionic surfactant (NPE with water/fibresand NPE/fibres ratios 50 w/w and 0.03 w/w respectively; then the samples were rinsed twice in demineralised water.A second series of samples was coated with PPy producedby an in situ chemical polymerisation in aqueous solutions.In the PPy

24、 deposition, the fibres were placed in a stirred aqueous solution containing FeCl 3, NDS and non-ionic surfactant for about 15 minutes. After the monomer was added,the solutions became black in a few minutes and the stirringwas stopped. The concentrations of the polymerisation bath were 0.105 M of F

25、eCl3, 0.0175 M of NDS and 0.05 M ofmonomer (Py. The samples were pulled out from the solutionafter 5 h, rinsed in water and dried. PPy coated wool fibreswere industrially spun and knitted, as reported elsewhere 1.Another lot of wool was treated without the dopant in thesame condition, in order to co

26、mpare the electrical conductivity.SEM investigation was performed with a LEO (LeicaElectron Optics 135 VP SEM, at an acceleration voltage of15 kV and at 18 mm working distance. The fibres were mounted on aluminium specimen stubs with double-sided adhesive tape and sputter-coated with a gold layer in

27、 rarefiedargon, using an Emitech K550 Sputter Coater, with a currentof 20 mA for 180 s.SEM-EDX analysis were performed by an Oxford InstrumentsModel 7060 Link ISIS interfaced to a PC using 4096 channelsin the range of 10 keV, with a preset integral of 16000 countsbetween 0.00 and 3.00 keV. X-ray mic

28、roanalysis was performedwith a dead time of about 25%, 400 pA probe current, 15kV accelerating voltage and 18 mm working distance.FT -IR spectra were acquired by means of a Thermo NicoletNexus spectrometer, by attenuated total reflection (ATR technique with the Smart Endurance accessory, in the rang

29、efrom 4000 to 550 cm1 with 100 scansions and 4 cm1 of bandresolution and normalized to the amide I band at 1630 cm1. Domestic and commercial washing fastness were evaluatedby an Original Hanau Linitest apparatus using the ECE detergent distributed by EMPA Testmaterials, according toEN ISO 105-C06:19

30、97 A1S. Abrasion tests were performedusing a Nu-Martindale abrasion and pilling tester from James Heal & Co., with a load of 12 kN, according to ENISO 12947-1:1998.Electrical resistance was measured in a conditioned laboratory(20o C, 65% RH by means of a digital Multimeter Escort170 connected wi

31、th the long sides of sample (8 cm×4 cmby 16 terminals.Results and DiscussionAnalysis of Blank Treated WoolHercosett ®, Basolan®, raw wool and Mohair fibre samples,treated for 1h with FeCl 3 and NDS in aqueous solution aspreviously described, and rinsed twice for 5 minutes in about400

32、ml of stirred demineralised water to eliminate the excessof reagents, showed an intense permanent yellowing.The SEM images of the fibres are reported in Figure 1. The surface of wool fibres consists of cuticle cells overlappingto form a structure like tiles on a roof. In Mohair fibres, thistypical s

33、caled structure is less emphasized and the surface issmoother because the cuticle cells are thinner. As can be noted, Hercosett® wool (a and Basolan® wool (b show nodamage of the cuticle cells, on the contrary of raw wool (cand Mohair fibres (d. The explanation may be that the acidicchlori

34、ne-based oxidation step in Hercosett ® and Basolan ®processes essentially modify the cuticle cells 20-23: raw wool(c and Mohair fibres (d, which were not previously treated,show the detachment of some cuticle cells, in accordance with literature which asserts that surfactants can have a si

35、gnificant influence on the reactions of wool to acids 15.Figure 2 shows the FT-IR spectra of NDS dopant powder,FeCl 3/NDS treated samples (thick lines and untreated wool(thin lines for comparison. NDS spectrum shows the typicalabsorption of aromatic sulphonates. The bands in the range1250-1000 cm1 c

36、an be attributed mainly to -SO3 groups and inparticular to the asymmetric and symmetric S=O stretchingvibrations, whereas the bands at 830, 660 and 620 cm1 canbe assigned to the aromatic C-H bending vibration absorptions.The spectra of the untreated samples (thin lines show thetypical featuring of k

37、eratins. Peptide group (-CONH- givespectral bands at 1630, 1520 and 1235 cm1 assigned to I, IIFT-IR Study of Dopant-wool Interactions During PPy DepositionFibers and Polymers 2006, Vol.7, No.2107 Figure 1. SEM images of FeCl3/NDS treated (a Hercosett wool (×3000, (b Basolan wool (×2000, (c

38、 raw wool (×1500, (d Mohair fibres(×1500.Figure 2. FT-IR spectra of NDS powder, untreated (thin line andFeCl 3/NDS treated (thick line wool: (a Hercosett wool, (bBasolan wool, (c raw wool, (d Mohair.and III amides, respectively. Finally, the spectra of FeCl 3/NDS treated samples show some

39、modification in the rangeof 12501000 cm1 and below 700 cm1. The positions of thesenew sharp peaks are in good agreement with the bands of theNDS. Moreover, the peak intensity of the sharp peak at 1030cm 1 decreases in the order: Hercosett ® wool > Basolan ®wool > raw wool > Mohair

40、 fibres. Thus, it seems that theNDS was absorbed onto the fibres, and in particular on Hercosett ® and Basolan ® treated wools. The band at 1390cm 1 attributed to -CH3 bending 25 strongly decreases inintensity in the spectra of the treated samples. Wool containsa large amount of amino acid

41、s with methyl-terminal side chain: Alanine (5.2%, Isoleucine (3.1%, Leucine (7.0%,Threonine (6.6%, Valine (5.5% and Methionine (0.4%. Thedisappearance of that band is probably due to conformationalrearrangements induced by acidic condition, which hind the-CH 3 symmetric bending mode.Samples of Herco

42、sett® wool were treated for 5h in aqueoussolution, as previously described, with FeCl3 or HCl or APSonly, and rinsed twice for 5 minutes in about 400 m l of stirred demineralised water. Only the fibres treated with FeCl3became yellow-brown. FT-IR analysis of these samples is reported in Figure

43、3. No significant modifications were noted inthe spectra of FeCl 3 6 (b and HCl treated (c Hercosett ®wools with respect to untreated (a Hercosett ® wool. The spectrum of APS treated (d Hercosett ® wool shows an absorption increase in the range 1140-1100 cm1 due to S-Ostretching of th

44、e oxidized species of cystine S-S bonds (Cys-S-S-Cys. In particular, the absorption bands at 1040, 1070and 1124 cm1 are assigned respectively to cysteic acid (Cys-108Fibers and Polymers 2006, Vol.7, No.2Figure wool, (c HCl treated wool, (d APS treated wool.3. FT-IR spectra of (a untreated wool, (b F

45、eCl 3 treated SO dioxide (Cys-SO3 H, cystine-S-monoxide (Cys-SO-S-Cys and cystine-S-with APS, not evidenced after the previous described treatment2-S-Cys 1,26-28 produced by the treatmentwith inorganic sulphate is centred near 1100 cmFeCl 3. On the other hand, the absorption 1it 26; therefore,band o

46、f absorption increase. The bands of cysteine-S-sulphonate (or is possible that some residues of APS contribute to the Bunte remain the same, as expected.salt, Cys-S-SO 3H at 1024 and 1190 cm1 1,26-28different Figure 4 shows FT-IR spectra of after NDS treatments lasting 5h Hercosett ®in aqueous

47、wool solution, after stirred demineralised water. The FT-IR spectrum (b of thebeing rinsed twice for 5 minutes in about 400 m l of sample treated with NDS does not show the NDS absorptionFigure wool, (c APS/NDS treated wool, (d HCl/NDS treated wool, (e4. FT-IR spectra of (a untreated wool, (b NDS tr

48、eated FeCl 3/NDS treated wool.Alessio Varesano et al.bands, indicating that the dopant is not absorbed by the wooland it is removed in consequence of the rinses. On the otherhand, the spectrum (c of APS/NDS treated Hercosett®shows weak absorptions in the range 1100-1000 cm1 woolto the cystine o

49、xidation (as previously reported, whereas the relatedspectra (d of HCl/NDS treated wool and (e of FeCltreated wool show sharp peaks at 1085, 1025, 660 and 6203/NDScm 1 and a broad band at 1175 cm 1NDS Hercosett (see ®Figure 2. Thus, the presence , already of NDS attributed onto the to solution

50、of FeClSamples wool seems to be promoted by an acidic pH.of Hercosett ® wool were treated for 1h with a in about 4003 and dopant, and rinsed twice for 5 minuteshighlighted that NS and DBS slowly react with ferric ionsm l of stirred demineralised water. It should beand form a gelatinous precipit

51、ate in about 3DS rapidly precipitate with FeClh. On the contrary,filtered and the clarified solution was used to treat the fibre3, hence the suspension wassamples. Figure 5 shows FT-IR spectra of the dopant powder(thin line and treated Hercosett®changes untreated one (a are reported in Table 1

52、and compared within the spectra of treated wool (thick line. The mainwool with respect to the peaks of the dopant powder. In the FeCltreated wool samples, it is interesting to note a shift at lower3/NDS and FeCl3/NSwavenumbers suggesting acidic condition (pH interactions of the symmetric between S-O

53、 dopants stretching and wool. vibrations, and the side-chains of wool keratins are in the cationic form< 4, the amino and carboxyl groupsIn the (H3N +interactions between keratin chains and anionic groups (-SO-wool-COOH, therefore this could promote electrostatic32of dopants. All the dopants test

54、ed in our experiments were absorbed or fixed onto wool, but solely the NDS is suitablefor the doped PPy deposition, due to its stability in solutionwith FeCl3.Figure 5.line and FeCl FT-IR spectra (a untreated wool, (b NDS powder (thinline and FeCl3/NDS treated wool (thick line, (c NS powder (thinlin

55、e and FeCl3/NS treated wool (thick line, (d DS powder (thinline and FeCl3/DS treated wool (thick line, (e DBS powder (thin3/DBS treated wool (thick line.FT-IR Study of Dopant-wool Interactions During PPy DepositionTable dopant treated wool related to some dopant peaks (see Figure 51. New absorption

56、bands in the FT-IR spectra of FeCl 3/DopantNew peaks (cmDopant peaks (cm1175118010851100NDS1025104566066062062011601180NS 1085110010251045DS120012151000900100090011701185DBS11301125104010451010 1010Analysis of PPy Coated Wooldescribed, PPy coated Hercosett® wool fibres, obtained as previouslypr

57、oducing electrically conducting fabrics with a cover factorwere industrially intersected, spun and knitted of 1.27 mm tex (according to Woolmark Test Method 169,good handle and a deep and even black colour.The fabric obtained from PPy coated Hercosett®NDS was tested for domestic and commercial

58、washing and wool withabrasion EDX microanalysis, FT-IR and SEM.resistance. Fabric samples were examined with EDX spectra are reported in Figure 6. In every sample,Figure treated wool, (c freshly PPy coated wool, (d knitted fabric from6. EDX spectra (a FeCl 3 treated wool, (b FeCl 3/NDSPPy washing te

59、st.coated wool, (e knitted fabric from PPy coated wool after Fibers and Polymers 2006, Vol.7, No.2 109gold is present due to sample preparation (sputter coatingand sulphur is naturally widely present in wool keratin. Thespectra (a and (b are related to FeClwool respectively. The spectrum (a shows a huge presence3 and FeCl3/NDS treatedof chlorine and iron; instead, the spectrum (b shows somepresence of chlorine and iron in traces. In addition, NS andDBS reported here for sake of brevity. The spectrum (c of freshlyshowed the same behaviour, but the spectra are not PPy Thus, i