Synthesis and characterisation of electrical conducting polymers co polymers based on omega functionalised 3 alkylthiophenes 4

Chapter Graft copolymers of polythiophene and PMMA 1. Introduction: As was discussed in the previous chapter, the properties of the graft copolymers of PS and polythiophene is affected by their backbone structure. The properties of the graft copolymers can be changed by altering or replacing the polythiophene and/or PS backbone structure. In this chapter, the different properties of the graft copolymers with poly(methyl methacrylate) PMMA and polythiophene backbones will be explored. These graft copolymers essentially have structures similar to PS and polythiophene graft copolymers. The main difference would be the presence of the PMMA in place of the PS backbone. Hence any property differences of the copolymers should be caused mainly by this change of structure. The idea of integrating PMMA and polythiophene into a copolymer system has interested many. A direct approach was to form linkages between thiophene or its derivatives and MMA to give block copolymers. This can be achieved by both chemical [1] and electrochemical methods [2]. The copolymers were reported to be soluble and conducting although these properties depend on the amount of thiophene moiety that could be integrated into the system. Poly(3-alkylthiophene) containing terminal acrylate or methacrylate functional group on the alkyl side chains have been reported. Such material can be copolymerised by radiation, either UV or electron beam, to produce highly cross-linked insoluble graft copolymers, which make these materials useful for photolithographic patterning [3-6]. Grafting of poly(methyl methacrylate) (PMMA) to polypyrrole and 131 polythiophene via an ester linkage has also been shown to give soluble graft copolymers with moderate conductivity [7a-d]. More recently the syntheses of PMMA and polythiophene or polypyrrole copolymers linked through ester linkage were reported [8a-b]. The PMMA and polythiophene graft copolymers prepared in this project will have PMMA and polythiophene backbones linked through alkyl chain linkages. These graft copolymers was made in a similar approach as described in the previous chapter for PS and polythiophene copolymers. A novel monomer of functionalised 3-alkylthiophene, which contained a terminal , -unsaturated ketone group, was synthesised. This monomer could be polymerised directly through a two-step reaction. It may also be copolymerised with MMA and thiophene in turn to give another graft copolymer. Similarly, this monomer can be copolymerised with MMA and 3-alkylthiophenes of different alkyl chain lengths to afford another two graft copolymers. The details of the experiments are described below. 132 2. Experiment: 2.1 Monomer synthesis: The synthesis of the novel monomer is depicted in the following scheme: Grignard Rxn Triphenylphosphine HO CH2 Br CH2 Bromine CH2 S SeO2/tBHP O CH2 Scheme 4.1 CH2 Charcoal S OH KMnO4 S Synthesis of monomer Starting material 1-hydroxylundec-10-ene (1) was brominated in excess bromine and triphenylphosphine with high yield. The brominated product was then coupled with 3-bromothiophene through Grignard reaction. As reported in literature [9], this straightforward reaction gave high yield although a small amount of 2, vinyl isomer (11-bromo-undec-2-ene) was detected together with compound (see scheme above). The oxidation step using selenium dioxide was less straightforward. SeO2 has been known as an effective alkene oxidising agent that forms alcohol and/or , , -unsaturated -unsaturated carbonyl products [10]. The reagent is particularly interesting to many organic chemists due to its regio- and stereo133 specific nature [11, 12]. These reports described that the reaction gave higher yield when the double bond groups were more substituted, as well as the use of stoichiometric amounts of SeO2 with excess t-butylhydroperoxide (tBHP) to maintain the selenium in the reactive Se (IV) oxidation state. Moderate yields of allylic alcohol could still be obtained from the less substituted alkenes. Another report described a method of selective oxidation of primary allylic alcohols to , -unsaturated aldehydes [13]. In that experiment, an oxidsing reagent of SeO2/tBHP/SiO2 was used instead of the traditional MnO2 oxidising agent to oxidise alcohol into aldehyde. It was hoped that applying the reagent mentioned in Kalsi et al.’s paper [13] would directly oxidise 3-(unde-10-enyl)thiophene (3) to 11-thiophen-3-yl-undec-2-enal, as shown below. CH2 CH2 SeO2/tBHP/SiO2 S S O 11-thiophen-3-yl-undec-2-enal The main difficulty expected was that the mono substituted alkene has low reactivity towards such oxidising agent. True enough, when the reaction was carried out, a large portion of the starting material remained unperturbed. There were no major products, although the expected aldehyde was detected using NMR. Other products formed include the , -unsaturated ketone. The reaction was repeated a few times under different conditions. Although a higher percentage of the mono substituted alkene could be oxidised, there were still no major products. Hence this reaction route was abandoned for the more ‘traditional’ two-step oxidation method. 134 In the first step, the ratio of SeO2: tBHP: alkene used was 0.5:2:1. A mixture of oxidised products was formed as expected. The reaction mechanism suggests that the terminal unsaturated allylic alcohol should be the major product, as illustrated below: t t O Bu O HO O Bu O O Se HO H H C H OH Se H (CH2)7-TH H H H H H H (CH2)7-TH C H+ H O H HO (CH2)7-TH C H H (CH2)7-TH C H H O H Se O HO t Se t O O Bu HO O Bu H (CH2)7-TH C H OH H Scheme 4.2 Possible mechanisms for the formation of as the major product The complex formed by SeO2 and tBHP kept the selenium centre at a higher oxidation state of IV [11, 12], which made it prone to nucleophilic attack from the alkene groups. There are two possible sites of attack, namely positions and 135 (see scheme above). Attack at position would form a six-membered ring transition state, which would result in a stabilised allylseleninic ester transition state with a di-substituted double bond. Subsequent C-Se bond rotation and sigmatropic rearrangement would give an ester that was readily hydrolysed by tBHP to form the alcohol. At the same time, the oxidising agent would be regenerated. This is a thermodynamically favoured reaction route. OtBu O O Se OH H (CH2)7-TH C H H H H The alternative attack is at position 2. At the intermediate stage, the adjacent alkyl group may help to stabilise the electron poor carbon compared to the attack at position 1, as shown below: t O Bu O HO Se OH H C (CH2)7-TH H H H H 136 This might lower the activation energy for the reaction to take place. However, such an attack would also lead to a carbocation transition state that is highly unstable. Continued rearrangement of this intermediate would lead to an allylic alcohol with a terminal alcohol that could be one of the minor products. Further oxidation of the alcohol would result in an aldehyde. As mentioned earlier, some , - unsaturated aldehydic product was detected when was oxidised with SeO2/tBHP/SiO2. The abovementioned reaction intermediate might have contributed to the formation of that product. The oxidation reaction of using SeO2 and tBHP in 0.5 to ratio was usually allowed to react overnight. About 50% of the starting material was recovered in most cases. Prolonged reaction time did not improve the yield much. Moreover, more side products were produced thus creating complications during purification. In the second oxidation step, a more conventional oxidising agent was prepared by adsorbing KMnO4 on charcoal, as described in literature [14]. The reaction gave the desired product in moderate yield (~35%). 137 2.2 Copolymers syntheses: The first step was carried out by polymerising using AIBN as initiator to give 6. Polymer was then oxidatively polymerised with FeCl3 to yield graft copolymer 7, as shown below: O CH2 AIBN CH2 n FeCl O S S Scheme 4.3 CH2 S n O m Synthesis of graft copolymer from monomer The precursor polymer formed after the first step was a sticky solid that could be dissolved in solvents such as CHCl3 and CCl4. After the second polymerisation step, the resultant polymer was found to be insoluble. It seemed to ‘swell’ in the solvents, a sign of cross-linkage in its structure. In order to obtain a more processable copolymer, the monomer was first copolymerised with MMA in 1:9 ratio using AIBN as initiator. The precursor copolymer (8) obtained was dissolved in CCl4 and further copolymerised with thiophene in a 1:9 ratio to give graft copolymer 9. It was also copolymerised with 3-butylthiophene in a 1:9 ratio to yield graft copolymer 10. Similar to the case for PS graft polythiophene as discussed previously, the conductivity and solubility of the graft copolymer containing 3-butylthiophene improved drastically. The precursor copolymer (8) was also copolymerised with 3-dodecylthiophene in 1:9 ratio using the same method to produce graft copolymer 11. The effects of chain 138 length on the properties of the graft copolymers can be investigated by comparing the properties of copolymers 10 and 11. O CH2 CH2 AIBN CH2 MMA S O O CH3 CH2 OMe CH3 CH2 S S S S CH2 n FeCl3 Scheme 4.4 O CH2 O O m Synthesis of graft copolymer CH2 AIBN CH2 MMA S CH2 n OMe O O CH3 CH2 OMe CH2 3-alkyln thiophene FeCl3 S CH3 CH2 CH2 S S O O m H3C (H2C) x Scheme 4.5 10 (x=4), 11 (x=10) Syntheses of graft copolymers 10 and 11 139 OMe n CH3 CH2 CH2 S S O O CH2 n OMe m This slight structural difference between copolymer and copolymer did not seem to have a big effect on their thermal stability in N2. The copolymers degraded as though they consisted of a single component only. This could indicate that the alkyl linkage between the two backbones was not the weak point in the copolymers’ structures. CH2 S Fig. 4.17 m n O TGA plot of copolymer in N2 environment The TGA plots for copolymers 10 or 11 are shown below: 166 Fig. 4.18 TGA plot of copolymer 10 in N2 Fig.4.19 TGA plot of copolymer 11 in N2 The onset temperature for degradation of copolymers 10 and 11 were slightly lower than that of copolymer 9. There is also an extra degradation step. Compared 167 to copolymer 9, copolymers 10 and 11 have large amounts of free alkyl side chains in their structure. Since all other conditions were similar, these dangling pendant groups may be the cause of the extra degradation step as well as the lowered thermal stability for these two copolymers in N2. However, as the thermal degradation products were not studied, this assumption cannot be proven yet. The thermal degradation pattern of this series of copolymers in air were more complicated, as shown in the stacked TGA plots for copolymers 7, 9, 10 and 11 below. They have similar thermal stability, although copolymers and seem to be slightly more stable under thermal oxidative conditions than copolymers 10 and 11. Table 4.9 summarises the thermal analyses results for this series of copolymers. Table 4.9 Thermal analyses results for copolymers 7, 9, 10 and 11 Co-polymers Onset temp (oC) Complete temp (oC) Percentage residue Tg (oC) 248 555 1.62% -- 243 564 1.11% 72 10 235 603 1.94% 54 11 232 650 1.08% 71 168 Fig. 4.20 Stacked TGA Deriv. Weight (%/min) plots for copolymers 9, 10 and 11 The thermal oxidation of this series of copolymers in air will not be further analysed here due to their complicated degradation patterns and the lack of data on their decomposed side products. These degradation patterns are likely to be related to the complex structure of the copolymers and may be worthy of further investigation in another project. 169 3.2.8 SEM and EDX The SEM images of the four graft copolymer powders are shown below. SEM images of copolymers and depict the polymers’ small and porous particles. On the other hand, copolymers 10 and 11 contain particles with larger microstructures. Fig. 4.21 SEM image of (from top to bottom, left to right) copolymers 7, 9, 10 and 11 The atomic ratio that was calculated based on EDX spectra of the four graft copolymers are listed as follow: 170 Table 4.10 Atomic ratios of copolymers 7, 9, 10, 11 calculated based on EDX spectra Copolymers Atomic ratio C (%) Atomic ratio S (%) Atomic ratio O (%) Calculated formula 10 11 86.6 77.0 79.1 84.5 6.78 8.82 6.55 5.72 6.61 14.2 14.4 9.8 C13OS C87O17S10 C121O22S10 C148O17S10 Elemental analysis formula C15.5H21.8O1.4S C92H126O16S10 C112H152O17S10 C202H305O25S10 The very high oxygen content that was indicated in XPS analyses for copolymer was not observed on the EDX spectrum. This result is in agreement with the elemental analysis results of this copolymer. Conclusion could be drawn that if oxidation of this compound did occur as suggested by XPS, such reaction was restricted to the outer layer of the material. The results for the other three copolymers showed that the S to O ratio was close to 1: 1.9 (the monomer feed ratio). 171 3.2.9 Conductivity study The maximum conductivities attained by the graft copolymers are listed in the table below. The amount of dopant absorbed by the copolymers at the maximum conductivity in percentage weight increase is also shown. Table4.11 Maximum conductivity achieved by the copolymers 7, 9, 10, 11 Co-polymers 10 11 Maximum conductivity (S/cm) 9.8x10-4 0.86 2.8 3.3 Percentage weight change (%) 178 95 133 88.7 As expected, graft copolymer was not conductive. After taking up almost twice as much I2, it can only achieve a maximum conductivity of about 10-3 S/cm. However this was still much better than the PS and polythiophene copolymer formed in a similar way, as was discussed in the previous chapter. Copolymer 9, although not very soluble, possessed rather good conductivity that can be compared to that of pure polythiophene. Conductivities for both copolymers 10 and 11 were good. The doping level of 10 was higher than 11 probably due to its higher polythiophene content, which meant increased dopant uptake was necessary for it to achieve maximum conductivity. Copolymer 11 achieved the highest conductivity in this series of copolymers despite having the lowest percentage molecular weight of the thiophene unit. It appears that the length of the alkyl side chain would help the copolymers achieve improved electronic 172 properties, since the main structural difference between copolymers 10 and 11 is the alkyl pendant chain length. It should be noted that cross linkages most likely exist in the structure of this series of copolymers as a result of the two-step polymerisation method. This is especially true in the case for copolymer judging from its properties and maybe to a lesser extent for copolymers 9, 10 and 11. This point will be further illustrated in Chapter of this thesis. 173 Conclusion: The graft copolymer of PMMA and polythiophene joined through alkyl linkages has been synthesised. NMR and FT-IR analyses confirmed their structures and functional groups. Elemental analyses revealed their bulk elemental composition and XPS indicated surface elemental composition. These copolymers exhibit better processibility compared to PS and polythiophene copolymers formed in a similar manner. There are also marked improvements in their conductivity. This series of graft copolymers were also found to be thermally stable. Therefore, these materials can be useful as potential anti static material. 174 Experimental 1-hydroxylundec-10-ene, AIBN, thiophene was used as purchased from SigmaAldrich. THF and ether were distilled from Na wires. CHCl3, hexane, CH2Cl2, methanol, ethanol and acetone were distilled. The 3-alkylthiophenes were synthesised using the method described in the previous chapter. The “active” manganese dioxide was prepared according to the method described by L. A. Carpino [14]. In a typical experiment, a solution of 20 g of potassium permanganate in 250 ml of water was stirred at room temperature with 10 g of activated carbon for 16 hr. The mixture was then filtered and the precipitate obtained was washed four times with 50 ml portions of water and spread out to dry in air. The air-dried solid was then put in an oven set at 105oC for 24 hrs before it was used. 1-bromoundec-10-ene Added to dry dichloromethane (800 ml) in order are: triphenylphosphine (210g, 800mmol) and bromine (128g, 800 mmol). A solution of 1-hydroxylundec-10-ene (45g, 266 mmol) in dry dichloromethane was added and the mixture was stirred at room temperature under nitrogen atmosphere for hr. The disappearance of the alcohol and formation of the alkyl bromide was monitored by TLC. When the reaction reaches completion, the solvent was removed by the rotary evaporator and the crude product was then purified by column chromatography. The yield was 55g (212 mmol), or 88% percentage yield. 175 H of 1-bromoundec-10-ene 1.25-1.47 (12H, br m,), 1.70 (2H, br quintet), 3.39 (2H, q), 4.92-5.03 (2H, m), 5.78 (1H, ddt) 3-(unde-10-enyl)thiophene A solution of 1-bromoundec-10-ene (11.1g, 61 mmol) in dry diethyl ether (15 ml) was added dropwise to a stirred suspension of magnesium turnings (1.49g 61 mmol) in dry diethyl ether (5 ml) and stirred for hr at room temperature. The grey solution was transferred via cannula to a dropper funnel and was added dropwise to a suspension of NiCl2(dppp) (0.11 g, 0.20 mmol, 0.45 mol%) and 3bromothiophene (7.3 g, 45 mmol) in dry diethyl ether (15 ml), where a gentle reflux was maintained. The solution was then stirred for days at room temperature and carefully quenched with saturated NH4Cl solution. The organic layer was washed with water and brine, dried and the solvent removed to give an orange liquid. Distillation (Kugelrohr, 100-130oC, 0.1 mmHg) gave 7.7g of colourless oil. Analysis showed that this is a mixture of 3-(undec-10-enyl)thiophene (~96% in mixture) and 3-(undec-9-enyl)thiophene (~4% in mixture). The percentage yield is ~71%. (Found: C, 76.4; J, 10.5. C15H24S requies C, 76.2; H, 10.2%); vmaz(CHCl3)/Cm-1 3060w (alkene CH), 2900s, 2840s (alkane CH), 2630w (C=C), 1440 m (thiophene), 990 m and 910s (RCH=CH2); H of 3-(undec-10-enyl)-thiophene 1.20-1.45 (12H, br m,), 1.62 (2H, br quintet, J ~7.4), 2.02(2H, q, J 6.7), 2.62 (2H, t, J 7.7), 4.90-5.04 (2H, m), 5.82 (1H, ddt, J 17.0, 10.2 and 6.7), 6.93 (2H, m) and 7.23 (1H, m). 176 11-thiophen-3-yl-undec-1-en-3-ol Into a 250 ml flask, 5.5 g (0.05 mol) of SeO2, 75 ml of CH2Cl2 and 22 ml (0.2 ml) of 90% tert-butyl hydroperoxide (tBHP) was introduced. After the mixture had been stirred for 0.5 hr at 25oC (water bath), 25g (0.1 mol) of 3-(unde-10enyl)thiophene was added over several minutes. The mixture was stirred at 25oC for hr (reaction monitored by TLC). Benzene (50 ml) was added and the CH2Cl2 was removed on a rotary evaporator. Ether (100 ml) was added and the organic phase was washed four times with 25 ml of 10% KOH and once with brine. The solution was dried with anhydrous MgSO4 and filtered before the solvent was removed to afford a yellowish liquid as crude product [17]. About 9.5 g of product was obtained as colourless oil after repeat column chromatography using a mixture of CHCl3 and hexane as solvent, which gave a yield of 38%. H of 11-Thiophen-3-yl-undec-1-en-3-ol 1.30-1.62 (25H, br m,), 2.62 (2H, t, J 7.7), 4.04-4.11 (1H, m), 5.08-5.24 (2H, dd, J 24, 9) 5.83 (1H, m), 6.93 (2H, m) and 7.23 (1H, m). 13 C NMR of 11-Thiophen-3-yl-undec-1-en-3-ol 143.2; 141.3; 128.2; 124.9; 119.7; 114.5; 73.2; 37.0; 30.5; 30.3; 29.4 29.3; 29.2; 25.2. Found (C, 71.37; H, 9.58; O, 6.34; S, 12.70) 11-Thiophen-3-yl-undec-1-en-3-one To a 100 ml RBF, 23 g of active manganese dioxide and 60 ml CH2Cl2 solution of 11-thiophen-3-yl-undec-1-en-3-ol (2 g, 8.7mmol) was introduced. The mixture 177 was stirred overnight at room temperature before being filtered. The solid was washed with CHCl3 and the combined organic layers were washed with three portions of 50 ml water and brine before the solvent was evaporated to afford crude products. Several rounds of column chromatography was then carried out and gave 0.63 g (2.5 mmol) of the product as a colourless oil (percentage yield of 29%). H of 11-Thiophen-3-yl-undec-1-en-3-one 1.30 (10H, br m,), 1.61 (4H, br, m), 2.54-2.64 (4H, m), 5.80 (1H, d) 6.18-6.40 (2H, m), 6.92 (2H, m) and 7.23 (1H, m). 13 C NMR of 11-Thiophen-3-yl-undec-1-en-3-ol 200.1 143.1; 136.6; 128.2; 127.7; 124.9; 119.7; 39.6; 30.5; 30.2; 29.3; 29.2; 23.9 Found (C, 71.95; H, 8.86; O, 6.39; S, 12.81) Two-step polymerisation of 11-thiophen-3-yl-undec-1-en-3-one Step 1: To ml THF solution of 11-thiophen-3-yl-undec-1-en-3-one (0.4g, 1.83 mmol) 0.003g of AIBN was introduced. The reaction vessel was charged with N2 and stirred for 48 hr to afford a sticky yellowish solid. The crude product was washed with methanol and hexane before being dried in vacuum to afford 0.35 g of yellow solid. Step 2: This precursor polymer was then dissolved in 10 ml of CCl4 and the solution cooled to ~2oC under N2 atmosphere before 20 ml CH3NO2 solution of FeCl3 (0.9g, 5.49 mmol) was added dropwise in about 20 mins. Subsequently, the 178 mixture was stirred for ½ hr before it was poured into methanol. The precipitate obtained was filtered and soxhlet extracted with MeOH and acetone in turn. Yellowish powder was then dried under vacuum to afford 0.18 g of product. Copolymerisation of MMA and 11-thiophen-3-yl-undec-1-en-3-one About 12 ml of THF was used to dissolve 0.99 g (9.9 mmol) of MMA and 0.24 g (1.1 mmol) of 11-thiophen-3-yl-undec-1-en-3-one. The initiator, AIBN (0.01 g, 0.05 mmol) was added. Then the mixture was refluxed under N2 atmosphere for 48 hr before it was poured into MeOH. The white precipitate obtained was filtered and washed with hexane and MeOH before it was dried in vacuum. This precursor copolymer was used for further copolymerisation processes with 3- butylthiophene, 3-hexylthiophene and 3-dodecylthiophen following the procedure described above for the Step polymerisation of 11-thiophen-3-yl-undec-1-en-3one (Found: C 70.96%, H 8.30%, S 12.14%) IR/cm-1 (3090.14 w, 2926.67 s, 2851.89 s, 1709.30 s, 1456.47 m, 1364.09 w, 1080.65 w, 835.20 w, 746 w) (Found: C 61.02%, H 6.97%, S 17.68%) IR/cm-1 (3060.14 w, 2997.67 s, 2945.89 s, 1727.30 s, 1447.47 m, 1388.09 w, 1143.65 s, 927.12 m, 785 m) 10 (Found: C 64.37%, H 7.28%, S 15.32%) IR/cm-1 (3060.14 w, 2925.67 s, 2856.89 s, 1728.30 s, 1452.74 m, 1378.68 w, 1146.52 s, 831.20 m, 746.60 m) 11 (Found: C 70.35%, H 8.85%, S 9.29%) IR/cm-1 (3060.14 w, 2922.70 s, 2852.33 s, 1729.97 s, 1457.69 m, 1238. 68 w, 1147.66 s, 837.10 m, 752.26 m) 179 References 1. (a) Nalwa, H. S.; polymer, 32(4), 1991, 745-750 (b) Nalwa, H. S.; Thin Solid Film, 235: (1-2), 1993, 175-181 2. Iraqi, A.; Irvin, A. M.; Walton, J. 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J.; Spiegel, D.; Kim, Y.; Hotta, S.; Heeger, A. J.; Synth. Met. 28, 1989, C419 21. Kawai, T.; Nakazono, M.; Yoshino, K.; Technol. Rep. Osaka Univ. 42, 1992, 297 22. Chen, T.; Wu, X.; Rieke, R. D.; J. Am. Chem. Soc. 117, 1995, 233 23. Ng, S. C.; Xu, J. M.; Chan, H. S. O.; Macromolecules, 33, 2000, 7349-7358 181 [...]... of copolymer 7 (direct two step polymerisation of monomer 5), copolymer 9 (graft copolymer of monomer 5, MMA and thiophene), copolymer 10 (graft copolymer of monomer 5, MMA and 3- butylthiophene) and copolymer 11 (graft copolymer of monomer 5, MMA and 3- dodecylthiophene) (see Fig 4. 8) The spectra of the four copolymers were quite similar due to the similarities in their structures The bands between 31 00 -30 00... C 132 H182O19S10 40 .3 35.2 10 C202H305O25S10 C204H 344 O19S10 24. 4 24. 8 11 a The formulae were calculated using the amount of S as standard (meaning the content of other elements were normalised using the sulphur content) b The amount of oxygen was obtained by subtracting 1 with the sum of the content of other elements c The feed ratio for copolymers 9, 10 and 11 were monomer 5 : MMA : thiophene(for 9) /3- alkylthiophen(for... n 8 O m 7 Fig 4. 11 C1s core level of copolymer 7 The core level data for the other two copolymers are also listed as follows: Table 4. 5 C1s core level data of copolymer 9 Peak 0 1 2 Table 4. 6 Position (eV) 2 84. 6 285.7 287.9 Area 36 52 150 746 FWHM (eV) 1.9 74 1.79 7.207 C1s core level data of copolymer 10 Peak 1 2 3 Position (eV) 2 84. 6 285.7 287.9 Area 541 7 282 43 0 FWHM (eV) 1.899 1. 747 4. 201 158 As expected,... 28.1% 10 251 40 .1% 4 43 38.9% 20.9% 11 268 71.9% 48 7 21.6% 7.21% 13. 6% The thermal degradation patterns for these copolymers in an inert environment were simple Both copolymers 7 and 9 degrade in one step TGA plot of copolymer 7 is shown in Fig 4. 17 The thermal degradation of these two copolymers started at about 30 0oC and was complete at about 500oC Copolymer 7 had a closely linked backbone structure... 3. 2.5 XPS The XPS of the four copolymers revealed lines of C 1s, O 1s and S 2p An example of the XPS for copolymer 9 is shown below: CH3 CH2 CH2 8 S S O O CH2 n OMe m 9 Fig 4. 9 XPS spectrum of copolymer 9 The elemental content on the surface of the copolymers as analysed by XPS are listed in the table below: Table4.2 Copolymers 7 9 10 11 Summary of XPS elemental content of the copolymers O 1s (%) C... copolymer 7 160 O CH3 CH2 CH2 8 S S O O CH2 n OMe m 9 Fig 4. 14 XRD spectrum of copolymer 9 CH3 CH2 CH2 S S H 3C Fig 4. 15 8 CH2 O O OMe m (H2C) 4 10 XRD spectrum of copolymer 10 161 n CH3 CH2 CH2 S S H 3C Fig 4. 16 8 CH2 O O n OMe m (H2C) 11 11 XRD spectrum of copolymer 11 A summary of the 2 peaks is listed in Table 4. 7 Table 4. 7 Summary of the 2 peaks of the copolymers 7, 9, 10, 11 Co -polymers 2 peaks... produce a co- polymer that was soluble Hence no NMR analysis can be carried out for 7 The copolymerisation of the monomer with MMA and thiophene/ 3alkylthiophenes, on the other hand, generated largely soluble co -polymers A typical spectrum of one of these polymers, the graft copolymer of monomer, MMA, and 3- butylthiophene (10) is shown below: CH3 CH2 CH2 S 8 S H3C O O CH2 n OMe m (H2C) 4 10 Fig 4. 7 1 H... 9 .4 16 .4 12.5 10.2 86 .4 74. 8 80.2 85 .4 4.5 8.7 7 .3 4 .3 Element ratio C19O2S C86O19S10 C110O17S10 C199O24S10 Elemental analysis formula C15.5H21.8O1.4S C92H126O16S10 C112H152O17S10 C202H305O25S10 155 The high oxygen content on the surface of copolymer 7 was unexpected This may reflect the surface oxidation of this copolymer The high ester content that was suggested by NMR and elemental analyses for copolymer... caused by the presence of a small amount of ketone groups that originated from monomer 5 Fig 4. 8 Overlaid IR spectra of copolymers 7, 9, 10 and 11 Thiophene aromatic ring C-C stretching bands were evident on the spectra of all copolymers at around ~ 145 6 and ~ 137 0 cm-1 The lack of ester groups in copolymer 7 was once again noticeable due to the absence of the bands at 1 238 - 151 1 146 cm-1 attributed to... 2. 63 ppm owing to the –CH2 group next to a thiophene ring The multiplets at around 6. 93 and 7. 24 ppm confirmed the presence of thiophene groups All are evidence that the substitution of Br by thiophene have taken place The isomerisation of the double bond is verified by the weak band at 5 .48 ppm 140 CH2 S Fig 4. 1 9 3 1 H NMR of 3- (unde-10-enyl)thiophene (3) The 1H NMR of 11-thiophen -3- yl-undec-1-en -3- ol . OMe n AIBN MMA S CH 2 8 O CH 2 CH 3 CH 2 O OMe n S m (H 2 C)H 3 C x FeCl 3 3-alkyl- thiophene 5 8 10 (x =4) , 11 (x=10) Scheme 4. 5 Syntheses of graft copolymers 10 and 11 140 3. Result and Discussion: 3. 1 Monomer. The 13 C NMR spectrum (Fig. 4 .3 ) also confirmed the presence of the allylic alcohol. The ethylene carbons caused peaks at 1 43 and 141 ppm, whereas the deshielded hydroxyl group connected. and thiophene /3- alkylthiophenes, on the other hand, generated largely soluble co -polymers. A typical spectrum of one of these polymers, the graft copolymer of monomer, MMA, and 3 - butylthiophene