Synthesis of Poly(bis-3,4-ethylenedioxythiophene methine)s with Side-Chain Comprising Electro-Optical Moieties and Alkyl Chain Effect in Solid State Polymerization

PEI Tong PENG Kai CAI Xin-Yi YUAN Liang-Jie XIA Jiang-Bin

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Synthesis of Poly(bis-3,4-ethylenedioxythiophene methine)s with Side-Chain Comprising Electro-Optical Moieties and Alkyl Chain Effect in Solid State Polymerization

PEI Tong PENG Kai CAI Xin-Yi YUAN Liang-Jie*XIA Jiang-Bin*

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New poly(bis-3,4-ethylenedioxythiophene methine)s derivatives with typical electro-optical moieties of thiophene, carbazole and fluorene as the side chains are obtained by facile solid state polymerization (SSP) or melt state polymerization (MSP). Detail characterizations of these polymers are carried out and some key monomers? crystals are obtained for structures analysis. It is found that existence of alkyl chains decrease monomers onset temperatures for SSP (onset) due to the weakening of the intermolecular interaction in crystals.

Poly(bis-3,4-ethylenedioxythiophene methine)s derivatives; Solid and melt state polymerization; Alkyl chain effect

1 Introduction

Through rational design, polythiophene can be easily tailored, synthesized and be endowed with special and multi-functional properties for different applications1,2. Recently, a promising method of solid state polymerization (SSP)3–9including self-acid-assisted polymerization (SAAP)10–12, attracts much attention from academia due to its special features of solvent, oxidant or noble metal catalyzers free. For instance, the well-known poly(3,4-ethylenedioxythiophene) through SSP has been employed for photovoltaic devices of dye-sensitized solar cell13–15.

In addition, it is known that solid state polymerization (SSP) is a widely used method in industry16. Taking this into consideration, necessary investigation in this field is needed especially for the conjugated polythiophene synthesis. Though dozens of monomers5–12have been developed so far by longitudinal design strategy based on 3,4-ethylenedioxythio- phene (EDOT) or 3,4-ethylenedioxyselenophene molecule (EDOS), they need multiple synthesis steps due to the difficulty of modification on EDOT or EDOS molecules. Recently, we17–19and others20proposed a parallel design strategy with the substantial modification of polymer properties through main-chain, which may shed light on design and on the development of numerous monomers for SSP. Thus, a facile platform of EDOT-()-EDOT17is developed and corresponding quinonoid conjugated poly(3,4-ethylenedioxy- thiophene methine)s derivatives21–26would be obtained with excellent optical-electronic properties. However, some key issues are not clear, such as the accurate structures requirements for SSP, themonitoring of SSP process, rearrangement of repeat units conformation in polymer chains, the relationship between solid & melt state polymerization and so on.

Scheme 1 Synthesis of the monomers, corresponding polymers and digital imagines of SSP process.

In order to further broaden SSP?s scope and explore related application, it is necessary to effectively tune these conjugated polymers? photo-physical and chemical properties based on EDOT-()-EDOT platform. Moreover, through the modification on the side chain of CH2linker, the substitutions of R show their great effect on electrochemical and optical properties for the corresponding polymers19, which is not a common phenomenon for those traditional conjugated polymers. In addition, in order to obtain high molecular weight poly(3,4-ethylenedioxythiophene methine)s, alkyl chains are introduced and then these monomers are investigated under melt-state polymerization.

In this study, among optical-electronic fields & applications common moieties such as thiophene, carbazole and fluorene are introduced as the side chains and their corresponding poly(3,4-ethylenedioxythiophene methine)s derivatives’ photo- physical and electrochemical properties are carefully investigated as well. In addition, the alkyl chain effect on SSP and their molecule weight distribution under reaction conditions are investigated further.

2 Materials and methods

2.1 Materials

EDOT, thiophene-2-carbaldehyde, were purchased from J & K. 5-Iodo-2,3-dihydro-thieno[3,4-b][1,4]dioxine17–20,27, 5- butylthiophene-2-carbaldehyde28, 9-butyl-9H-carbazole-3- carbaldehyde29, 9,9-dibutyl-9H-fluorene-2-carbaldehyde30were synthesized according to previous reports.

2.2 Monomer synthesis

Monomers of I2-CH(R)-EDOT were synthesized in accordance to previous method31as shown in Scheme 1.

2.2.1 I2-Th-EDOT

White solid(37%),1H NMR:(CDCl3) 6.58 (d, 1H, thiophene―H), 6.57 (d, 1H, thiophene―H), 5.99 (s, 1H, ―CH), 4.25 (d, 2H, ―CH2), 4.18 (d, 2H, ―CH2), 2.74 (t, 2H, ―CH2), 1.59 (m, 2H, ―CH2), 1.36 (m, 2H, ―CH2), 0.92 (t, 3H, ―CH3).13C NMR:(CDCl3) 145.7, 144.1, 141.7, 137.5, 125.5, 124.4, 123.6, 65.5, 64.8, 47.8, 36.1, 33.85, 30.1, 22.5, 14.1.

2.2.2 I2-BuTh-EDOT

Yellow solid (35%),1H NMR:(CDCl3) 6.58 (d, 1H, thiophene―H), 6.57 (d, 1H, thiophene―H), 5.99 (s, 1H, ―CH), 4.25 (d, 2H, ―CH2), 4.18 (d, 2H, ―CH2), 2.74 (t, 2H, ―CH2), 1.59 (m, 2H, ―CH2), 1.36 (m, 2H, ―CH2),0.92 (t, 3H, ―CH3).13C NMR:(CDCl3) 145.7, 144.1, 141.7, 137.5, 125. 5, 124.4, 123.6, 65.5, 64.8, 47.8, 36.1, 33.85, 30.1, 22.5, 14.1. Anal. Calcd for C21H20I2O4S3: C, 36.75%; H, 2.94%; Found: C, 38.12%; H, 2.41%

2.2.3 I2-Carb-EDOT

Light yellow solid (40%),1H NMR:(DMSO-d6) 8.11 (d, 1H, Ar―H) , 7.96 (s, 1H, Ar―H), 7.56 (d, 1H, Ar―H), 7.52 (d, 1H, Ar―H), 7.44 (t, 1H, Ar―H), 7.27 (d, 1H, Ar―H), 7.16 (t, 1H, Ar―H), 5.92 (s, 1H, ―CH), 4.35 (t, 2H, ―CH2), 4.20 (d, 2H, ―CH2), 4.16 (d, 2H, ―CH2), 1.71 (m, 2H, ―CH2), 1.30 (m, 2H, ―CH2), 0.88 (t, 3H, ―CH3).13C NMR:(CDCl3) 143.7, 140.4, 139.3, 136.7, 131.1, 125.3, 125.1, 122.4, 122.3, 120.1, 119.1, 118.3, 108.3, 108.2, 64.9, 64.2, 46.8, 42.5, 40.4, 30.8, 20.2, 13.5. Anal. Calcd for C29H25I2NO4S2: C, 45.27%; H, 3.27%; N, 1.82%. Found: C, 46.85%; H, 3.412%; N, 1.75%.

2.2.4 I2-Carb-EDOT

Light yellow solid (40%),1H NMR:(DMSO-d6) 8.11 (d, 1H, Ar―H) , 7.96 (s, 1H, Ar―H), 7.56 (d, 1H, Ar―H), 7.52 (d, 1H, Ar―H), 7.44 (t, 1H, Ar―H), 7.27 (d, 1H, Ar―H), 7.16 (t, 1H, Ar―H), 5.92 (s, 1H, ―CH), 4.35 (t, 2H, ―CH2), 4.20 (d, 2H, ―CH2), 4.16 (d,2H, ―CH2), 1.71 (m, 2H, ―CH2), 1.30 (m, 2H, ―CH2), 0.88 (t, 3H, ―CH3).13C NMR:(CDCl3) 143.7, 140.4, 139.3, 136.7, 131.1, 125.3, 125.1, 122.4, 122.3, 120.1, 119.1, 118.3, 108.3, 108.2, 64.9, 64.2, 46.8, 42.5, 40.4, 30.8, 20.2, 13.5. Anal. Calcd for C29H25I2NO4S2: C, 45.27%; H, 3.27%; N, 1.82%. Found: C, 46.85%; H, 3.412%; N, 1.75%.

2.2.5 I2-Carb-C16-EDOT

Light yellow solid (40%),1H NMR:(CDCl3) 8.05 (d, 1H, Ar―H), 7.95 (s, 1H, Ar―H), 7.42 (d, 1H, Ar―H), 7.31–7.38 (m, 3H, Ar―H), 7.20 (d, 1H, Ar―H), 6.02 (s, 1H, ―CH), 4.25 (d, 2H, ―CH2), 4.16 (d, 2H, ―CH2), 4.14 (d, 2H, ―CH2), 1.85 (m, 2H, ―CH2), 1.24 (m, 26H, ―CH2), 0.86 (t, 3H, ―CH3).13C NMR:(CDCl3) 144.0, 140.7, 139.6, 137.0, 131.4, 125.6, 125.4, 122.7, 122.6, 120.4, 119.5, 118.6, 108.6, 108.5, 65.2, 64.5, 47.2, 43.1, 40.7, 31.8, 29.6, 29.5, 29.4, 29.3, 29.2, 28.9, 27.3, 22.6, 14.0.

2.2.6 I2-Flu-EDOT

Yellow solid (25%),1H NMR:(CDCl3) 7.66 (d, 1H, Ar―H), 7.61 (d, 1H, Ar―H), 7.29–7.31 (m, 3H, Ar―H), 7.21 (d, 1H, Ar―H), 7.18 (s, 1H, Ar―H), 5.86 (s, 1H, ―CH), 4.22 (d, 2H, ―CH2), 4.12 (d, 2H, ―CH2), 1.96 (m, 4H, ―CH2), 1.07 (m, 4H, ―CH2), 0.86 (m, 4H, ―CH2), 0.68 (m, 6H, ―CH3).13C NMR:(CDCl3) 150.9, 150.8, 143.9, 140.7, 140.3, 139.7, 137.2, 126.9, 126.6, 126.5, 124.6, 122.7, 122.4, 119.5, 65.2, 64.4, 54.8, 47.3, 41.1, 40.0, 26.8, 25.8, 22.9, 22.4, 14.1, 12.9.

2.3 General solid or melt state polymerization

The SSP procedure was followed according to previous method5–9,17–20. Due to the fact that hydrogenatom in CH2bridge was easily removed by the oxidant of iodine, the conjugated poly(bis-ethylenedioxythiophene methine)s with quinoidal structure were obtained. These polymers were further treated with hydrazine hydrate and afforded nearly fully dedoped respective polymers.

2.4 Crystal structure determination

Intensity data for all four crystals were collected using MoKradiation (= 0.07107 nm) on a Bruker SMART APEX diffractometer equipped with a CCD area detector at rt. Data sets reduction and integration were performed using the software package SAINT PLUS32. The crystal structure is solved by direct methods and refined using the SHELXTL 97 software package33.

2.5 Other characterizations

IR spectra for the characterization of the resulted polymers were recorded on a Perkin-Elmer FTIR spectrometer. Absorption spectra were measured on a Unicam UV 300 spectrophotometer at wavelengths from 300 to 1000 nm.Monomers were deposited by spin-coated or drop-casted with 0.5%–3% (mass fraction) of CHCl3monomers solution on fluorine doped tin oxide (FTO) substrate or slide glasses. These monomers coated substrate were employed for SSP and then resulted polymers or polymer/FTO substrates. These products were used for XRD, UV-Vis or as working electrode for electrochemical measurements. For the three-electrode electrochemical measurements in 0.1 mol?L?1LiClO4in acetonitrile, a 1 cm2area of FTO/Polymer substrate, platinum foil, and Ag/AgCl were served as the working, counter, and reference electrodes, respectively (CH Instruments 604D electrochemical system).X-ray diffraction (XRD) patterns were obtained by Bruker D8 advanced X-ray diffractometer by using Cu-Kradiation at room temperature. The molecular weight and molecular weight distribution of the polymers were determined by gel permeation chromatography (GPC) equipped with a Waters 2690 separation module and a Waters 2410 refractive index detector (Waters Co., Milford, MA).,-Dimethylformamide (DMF) was used as eluent at a flow rate of 0.5 mL?min?1with the temperature maintained at 30 °C, and the results were calibrated against polystyrene standards.

3 Results and discussion

3.1 Solid state polymerization results

According to the SSP results, all monomers can change into corresponding polymers smoothly and their SSP onset temperatures (onset) are not very high around 40–80 °C. It is interesting that after introducing butyl group, I2-BuTh-EDOT requires lower temperature of 48°C to trigger SSP while I2-Th-EDOT needsonsetof 62 °C. On the other hand, carbazole and fluorene substituted monomers have theironsetof 72 °C, 64 °C respectively. In addition, the introduction of longest hexadecyl chain results in a little bit higheronsetof 78°C. Though thiophene, carbazole and fluorene are rigid aromatic rings, theironsetare quite lower than those of benzene or naphene rings containing monomers based on the same platform19, which may due to the existence of alkyl chains. This interesting phenomenon is beneficial for the synthesis of those soluble polymers to meet the facile processibility and application requirements. Becauseonsetare definitely sensitive to corresponding monomers? structures, the detailed discussion will be done in the crystal analysis section as follows. In addition, taking similar properties for P(Carb-EDOT) and P(Carb-C16-EDOT) into account, P(Carb-EDOT) is chosen to measure its electro-optical properties while solubleP(Carb-C16-EDOT) is selected for its molecular weight information.

3.2 FTIR spectroscopy

FTIR spectra of the poly(3,4-ethylenedioxythiophene methine)s derivatives is shown in Fig.1. The absorption at 1475, 1434, 1360, and 1259 cm?1are signed to the stretching of C＝C and C―C in the thiophene ring34,35.Meanwhile, typical peaks around 704 cm?1, which are related to in-plane deformation of C―S―C of thiophene ring, are observed34. In addition, all polymers show distinct strong sharp peaks at 2956, 2926 and 2870 cm?1, which are assigned to CH3or CH2stretching modes36. In the case of P(Carb-EDOT), stretching mode at 1099 cm?1is observed due to the existence of C―N bond37.

Fig.1 FTIR spectra for these polymers.

3.3 XRD analysis

As we can see, I2-Th-EDOT shows typical crystalline phase with lots of sharp peaks at the range of 10°–40° and its XRD pattern is in consistent with its simulated results. However, other monomers show broad peaks at the scanned range. We attribute this interesting phenomenon to their amorphous phase at room temperature with the existence of alkyl chains. And it would show more crystal phase under low temperature.After SSP, polymers show broad peak around 25°, 23° and 24° for P(BuTh-EDOT), P(Carb-EDOT) and P(Flu-EDOT) respectively, which reflect their–stacking26distance of 0.356–0.386 nm between polymer chains. While in the case of P(Th-EDOT), it shows poor resolution peak in its XRD pattern as shown in Fig.2(a). It appears that alkyl chains of aromatic substitutions attached on CH(R) bridge are beneficial to chain packing in polymers matrix.

3.4 Absorption of polymers by SSP and hydrazine treated polymers

The dilute solution is prepared due to its small solubility of P(Th-EDOT). And all polymers? solutions absorption spectra are presented in Fig.3. As we can see, in the case of fresh made polymers solutions absorption spectra, most of them show peaks at 740–760 nm except that P(Carb-EDOT) exhibits a peak at shorter wave length of 670 nm, indicating of-type featured character. According to the observation of drastic drop of intensity at near-IR region around 600–1000 nm38,39, we obtained their neutral type polymers after hydrazine treatment. Briefly, compared with P(Th-EDOT) treated with hydrazine, the existence of butyl leads to the disappearance of peak at about 580 nm. At this moment, we cannot understand this interesting phenomenon, which may due to the poor conjugation by the steric effect. However, the introduction of carbazole and fluorene moieties result in a bathochromic peaks at longer wave length which is 612 nm and 640 nm respectively. Their detailed parameters of optical properties are summarized in Table 1. These results indicate that the modification on side chain in poly(bis-3,4-ethylenedioxy- thiophene methine)s matrix can change their optical properties, revealing these polymers’ great potential application in future optical-electronic devices application.

3.5 Cyclic voltammetry behavior of the polymers

As shown in Fig.4, the onset of oxidation potentials are 0.93, 0.57, 0.27 and 0.21 V (Ag/AgCl) for P(Th-EDOT), P(Th-Bu- EDOT), P(Carb-EDOT) and P(Flu-EDOT) respectively, indicating that the substitution moieties on CH2bridge have great influence on their electrochemical properties. It is noted that the introduction of butyl on thiophene results in the shift up of HOMO energy level because of the decrease of the initial onset potential of 0.36 V when compared with that of P(Th-EDOT).

Due to the observation of large reduction currents, we attribute these to the reduction process of oxidized polymer, i.e., these polymers can undergo a two-electron non-reversible oxidation processes40. In addition, except for P(Th-EDOT), other polymers show stable CV behaviors. In the case of P(Th-EDOT), as shown in Fig.4(a), its oxidation currents are not proportional to the scan rates. This special phenomenon indicates that additional electrochemical reaction occurs during the CV measurements. Taking the existence of non-conjugation parts41in the polymer chains into consideration, we believe CV measurements, especially during the anode scans, will result in the enhancement of conjugation parts in polymer chains. And this explanation is well supported by the fact that P(Th-EDOT) can show high initial oxidation potentials. Thus, in the existence of iodine under SSP, there are more non-conjugated parts in P(Th-EDOT) when compared with those carbazole or fluorene moieties containing polymers.

3.6 Crystallographic X-ray analysis

Monomers of I2-Th-EDOT and I2-Flu-EDOT structures and corresponding SSP pathways are presented in Figs.5–7. Interestingly, though alkyl fluorene moiety has bulkier size, I2-Flu-EDOT has similar molecule structure with I2-Th-EDOT, especially concerning of its intramolecular I/I, S/S distances and corresponding angles, as shown in Fig.5 and Table 2. We attribute this result to the fact that the fused ring of fluorene and its alkyl chains are far away from EDOT units, which has little steric effect on the ring of fluorene and its alkyl chains are far away from EDOT units, which has little steric effect on the single molecule framework.

As shown in Fig.6, monomer of I2-Th-EDOT has the first and the second closest Hal/Hal distance of 0.4397 and 0.4425 nm respectively (Table 3) with corresponding C13―C1 and C13―C1 contact distances of 0.5424 and 0.5244 nm respectively. And the third closest Hal/Hal distance of 0.6191 nm is observed with the shortest C―C (C13―C13) contact distance of 0.4910 nm. Thus, the first polymerization pathway along with-axil direction (formation of a helix between two columns of monomers, shown in Fig.6(c)) involves sole I/I distance of 0.4397 nm while the second polymerization pathway along with-axil direction (shown in Fig.6(d)) involves sole I/I distance of 0.4425 nm. Because these two pathways have similar key I/I distance and their corresponding C/C distances are 0.5424 nm and 0.5244 nm respectively. At this moment, we cannot determine which the preferred way is. For comparison, the shorter distance of 0.4397 nm is selected as the effective I/I distance as shown in Table 1.

Fig.2 XRD spectra of monomers and corresponding polymers.

Fig.3 Absorbance spectra of these polymers obtained by SSP and dedoped polymers by hydrazine treatment in CH2Cl2 solution.

(a) P(Th-EDOT), (b) P(BuTh-EDOT), (c) P(Carb-EDOT), (d) P(Flu-EDOT).

Table 1 Optical and electrochemical data of the obtained poly(bis-3,4-ethylenedioxythiophene methine)s.

aDetermined from the onset wavelength in the absorption spectra of solution samples (hydrazine treated) according to Fig.3, calculated bygap=1240/Abs.edge.bHOMO calculated byHOMO= ?(ox,onsetd+ 4.36) eV,cDetermined from HOMO levels and optical bandgaps.LUMO=HOMO+gap.dMake two tangents of the spinodal of oxidation curve, the value of intersection point isox,onset.

Fig.4 CVs of polymers films in acetonitrile solution containing 0.1 mol?L?1 Bu4NClO4 taken at various scan rates.

Fig.5 Intramolecular atoms distances and different angles in the monomers of I2-Th-EDOT and I2-Flu-EDOT.

While in the case of I2-Flu-EDOT (Fig.7(a)), the important Hal/Hal and related C―C contact distances are marked in the Fig.7(a, b). It is obvious that the first polymerization pathway along with-axil direction (Fig.7(c)) involves sole halogen distance of 0.5391 nm with the formation of a helix between sole columns of monomers. Though helix structures are observed by us19and other SSP system of quinodimethanes42, such polymerization pathway involving one column monomers is not very common among reported thiophene monomers. In this case, it may help to facilitate their helix formation. In addition, the second polymerization pathway is observed along with the same axil direction as shown in Fig.7(d) and it involves two I/I distance of 0.5650 nm and 0.8424 nm. Thus, the first pathway is the preferred one with the effective halogen distance of 0.5391 nm, which is quite long19among reported thiophene derivatives. It appears that the bulkier substitution can increase its effective halogen distances and also the C―C contact distance.

Table 2 Intramolecular atoms distances and angles.

Table 3 Selected I/I and C―C contact distances (nm) for the Reported Crystals.

aEffective Hal/Hal distance;b2of iodine: double van der Waals radius of iodine: 0.4 nm

Table 4 Effect of reaction condition on the molecular weight and PDI.

aMolecular weights and PDI were determined by GPC with respect to polystyrene standards.bDegree of polymerization (DP) was calculated based on thenvalues.cFraction soluble in DMF

It should be pointed out that taking SSP thermal requirement into consideration, such heat energy drives molecule reaction groups close together and construct corresponding C―C bond. Meanwhile, it drives molecule conformation, i.e. to reach repeat units equilibrium state. Therefore, we mainly discuss the effective halogen distance and ignore their inter-ring torsion angles between neighboring repeat units.

3.7 Dependence of effective I/I distances for alkyl-containing samples with their onset temperature of SSP

Though we failed to obtain I2-BuTh-EDOT crystal information, it shows loweronsetwhen compared with that of non-alkyl substituted I2-Th-EDOT. Moreover, as its effective halogen distance is up to 0.5391 nm, I2-Flu-EDOT shows quite lowonsetof 64 °C. Furthermore, our previous report20showed that I2-Pr-EDOT has a little bit loweronsetof 70 °C with its effective halogen distance of 0.4878 nm. Therefore, it appears that long alkyl chain would decreaseonsetdrastically. According to these interesting results, our previously proposed equation19of linear dependence of effective I/I distance withonsetneeds to be modified or refined. As for the fitted dotted line from those alkyl-chain samples, it gives an equation of= 19.4? 32.8 as shown in Fig.8 (data derived from those samples is presented in Table S2). Due to the lacking of enough crystals data at present, moderate R of 0.75 is obtained. Therefore, we can primitively deduce that the increasing 0.1 nm of effective I/I distance needs the elevatedonsetof 19 °C. It is lower than that from those non-alkyl chain samples19(0.1 nm for elevatedonsetof 26 °C). We noticed that I2-Carb(C16)- EDOT with hexadecyl chain shows a little bit higheronsetthan that of I2-Carb-EDOT with butyl chain, which might due to the larger effective halogen distance of the former.

In addition, alkyl chain would loweronsetaround 30 °C, revealing that non-harsh SSP condition is needed for monomers with alkyl chains. We think that this interesting phenomenon is from the possibility that alkyl chain will weaken molecule interaction especially those–stacking in crystal, which results in the decreasing ofonset. Furthermore, though it is generally accepted that the organic solid reaction usually occurs within 0.42 nm26between reaction groups distances, we have got several samples with quite long effective halogen/halogen distances over 0.5 nm. These exciting observations and their SSP success encourage us and reveal that SSP would be a very powerful means in the synthesis of conjugated polythiophene.

Fig.6 Single-crystal X-ray structure of compound I2-Th-EDOT.

(a) view of I/I distances (b) view of corresponding C/C contact distances (c) crystal packing viewed along the-axis, proposed the first polymerization pathway and involved I/I and C/C contact distances. (d) proposed the second polymerization pathway. The numbers indicate the corresponding distances in Angstrom. I, purple; S, yellow and C, gray.

Fig.7 Single-crystal X-ray structure of compound I2-Flu-EDOT.

(a) view of I/I distances; (b) view of corresponding C/C contact distances; (c–d) crystal packing viewed along the-axis, proposed the first and second polymerization pathways and involved I/I and C/C contact distances. The numbers indicate the corresponding distances in Angstrom. I, purple; S, yellow and C, gray.

Fig.8 Linear dependence of effective I/I distance with Tonset of SSP and the effect of alkyl chains.

Data of those non-alkyl chain samples derived from Ref.19.

3.8 Molecule weight information

Due to the poor solubility of other polymers, P(Flu-EDOT) and P(Carb-C16-EDOT) are selected for the detection of molecular weight and the results are listed in Table 4. Oligomers areobtained at low temperature under SSP. Previous studies18,19showed that SSP produces low molecular weight distribution because of the difficulty of the contact and reaction between their terminal groups of iodine atoms in oligomers during SSP procedure. However, large molecular weight of 19 K can be obtained for P(Carb-C16-EDOT) at 150 °C for three days under melt-state polymerization. It is noticed that high molecular weight of polythiophene derivatives are frequently obtained by melt state polymerization12,44. Therefore, low to high molecular weight can be well controlled through melt state polymerization, which is very important for their future application in other optical-electron fields.

4 Conclusions

In this work, typical electro-optical moieties of thiophene, carbazole and fluorene moieties are introduced to EDOT-()-EDOT platform and successfully employed in SSP. The results indicate that incorporation of desire moieties is a general means in fine tuning their corresponding polymers properties and paving their future application in photo-electronic devices. In addition, the introduction of alkyl chains would weaken intermolecular interaction and result in the drastically decrease ofonset. Furthermore, high molecular weight can be obtained through melt state polymerization.

Supporting Information:available free of chargethe internet at http://www.whxb.pku.edu.cn.

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固相聚合合成聚噻吩衍生物及烷基鏈對固相聚合的影響

裴 童 彭 凱 蔡心怡 袁良杰*夏江濱*

(武漢大學(xué)化學(xué)與分子科學(xué)學(xué)院，武漢 430072)

本文以EDOT--EDOT為基本模型，向側(cè)鏈引入噻吩、咔唑、芴等幾種典型的光電基團，并通過固相/熔融聚合得到相應(yīng)的聚合物。詳細探討了聚合物的相關(guān)性質(zhì)和幾種典型單體的晶體結(jié)構(gòu)，同時發(fā)現(xiàn)烷基鏈的引入降低了分子間的作用力，使得單體的初始聚合溫度(onset)降低。

聚噻吩衍生物；固相/熔融聚合；烷基鏈影響

O646

10.3866/PKU.WHXB201706071

May 8, 2017;

June 6, 2017;

June 9, 2017.

Corresponding authors.XIA Jiang-Bin, Email: jbxia@whu.edu.cn. YUAN Liang-Jie, Email: ljyuan@whu.edu.cn; Tel/Fax: +86-27-68756707.

The project was supported by the National Natural Science Foundation of China (21371138), the Funds for Creative Research Groups of Hubei Province, China (2014CFA007) and the Fundamental Research Funds for the Central Universities, China (2042015kf0180).

國家自然科學(xué)基金(21371138)，湖北省創(chuàng)新團隊科研基金(2014CFA007)及中央高?；究蒲袠I(yè)務(wù)費專項資金(2042015kf0180)資助項目