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Synthesis of novel copoly(styrene–maleic anhydride) materials and their luminescent properties
European Polymer Journal 39 (2003) 1091–1097 www.elsevier.com/locate/europolj
Synthesis of novel copoly(styrene–maleic anhydride) materials and their luminescent properties Chen Li, Xingang Pan, Chunfan Hua, Jianhua Su, He Tian
*
Institute of Fine Chemicals, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China Received 19 September 2002; received in revised form 14 November 2002; accepted 15 November 2002
Abstract Two series of new high fluorescent polymeric materials based on copoly(styrene–maleic anhydride) (SMA) were prepared by the condensation of SMA with fluorescent groups. One series consists of 1,8-naphthalimides derivatives that are linked with SMA. The other series were prepared by the condensation of SMA with 3,4,9,10-perylene tetracarboxylic mono-anhydride mono-imide. These simple routes to copolymer of styrene and maleic anhydride containing pendent luminescent moiety are promising in increasing fluorescent quantum yield in solid state and processing, in which styrene is employed as ‘‘diluents’’. The luminescent and the preliminary photovoltaic properties of these copolymers have been investigated. Ó 2003 Elsevier Science Ltd. All rights reserved. Keywords: Copolymer; Synthesis; Fluorescence; Perylene; 1,8-Naphthalimide
1. Introduction Polymer blending is widely used as a cost-effective way of producing new materials with customized properties. As polymer blends represent more than 30% of all plastics sold today and are amongst the most rapidly growing areas of polymer technology [1]. The copoly(styrene–maleic anhydride) (SMA) is a kind of polymer materials for commercial use. Lee et al. [2,3] first obtained it in 1979. Vermeesch [4] obtained chemical modified SMA with primary N-alkylamines by reactive extrusion. Because of its good properties and low cost, SMA is widely used in various areas such as automobile materials, electronic household applications etc. In recent years, because SMA can react easily with other compounds which have unique properties, many novel functional materials with the copoly(SMA) have emerged. And there is a widespread interest in polymeric luminescent materials, especially from the viewpoint of
*
Corresponding author. Tel./fax: +86-21-64252288. E-mail address: [email protected] (H. Tian).
excellent film-forming property and good solubility, which makes processing easier by simple spin coating. Meanwhile, to reduce the crystal density and lattice energy and increase the fluorescent quantum yield, many efforts have been made to incorporate the luminescent moiety into copolymers [5,6]. In this way, the chance of fluorescent quenching could be decreased as effort. Therefore, the copolymer of styrene and maleic anhydride containing pendent luminescent moiety would be promising in increasing fluorescent efficiency and processing, in which styrene is employed as ‘‘diluent’’ [7]. In this paper, we describe two approaches to get new fluorescent SMA polymeric materials with high quantum yield. The target compounds are shown in Scheme 1. In the first approach shown in Scheme 2, 3,4,9,10perylene tetracarboxylic mono-anhydride mono-imide [8–10] was condensed with hydrazine. The unsymmetrical perylene tetracarboxydiimide polymers were prepared by the condensation of the mono-imide intermediate with copoly(SMA). Dyes based on perylene 3,4,9,10-tetracarboxylic bisimides (PTCAs) draw much attention recently for used as the sensitizers of nanocrystalline semiconductors solar cells (Gr€ atzel type) with
0014-3057/03/$ - see front matter Ó 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0014-3057(02)00361-0
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C. Li et al. / European Polymer Journal 39 (2003) 1091–1097
Scheme 1. The molecular structures of novel fluorescent polymers.
O
O
N
O
O
O
O
O
N
NNH2
CoPoly(SMA)
NH2 NH2
O
R-PTCA
PSMIx
O
R-PTCM Scheme 2. Synthetic scheme of PSMI.
their outstanding chemical, thermal and photochemical stability [11,12]. PTCAs are highly absorbing in the visible to NIR (e 105 M1 cm1 ) and emit fluorescence with quantum yield near unity. It is crucially important for solar cell sensitizers to control the valence band since most of inorganic semiconductors such as SnO2 exhibit n-type character. A simple approach was to utilize two or more different dyes by a doping method, which show strong absorption at different wavelength and compensate absorbency. We used assembling idea and have explored some multi-chromophoric perylene compounds to extend the sensitizing spectral region with the maximum IPCE up to 24% [11b]. The results told us that perylene derivatives have good energy match with the
O
O
O
NH2NH2 R
O
energy band of SnO2 semiconductor. Therefore, some new perylene copolymers with good solubility have been developed here further and would be expected to be used for all-plastic solar cells application. The second approach (shown in Scheme 3) was based on 1,8-naphthalimide instead of 3,4,9,10-perylene tetracarboxylic mono-anhydride mono-imide. Naphthalimide derivatives have been widely used as brilliant fluorescent dyes in synthetic fiber technology and as electroluminescent materials [13–15]. The color including emission color of 1,8-naphthalimides can be tuned by substitution on the 4-position of the naphthalimide ring [16,17]. When suitable substituents were linked with spacers on the 4-position of the naphthalimide ring,
H2NN
CoPoly(SMA) R
O
NHSMIx NPSMIx NMSMIx NDSMIx NESMIx
Scheme 3. Synthetic scheme of NHSMI, NPSMI, NMSMI, NDSMI and NESMI.
C. Li et al. / European Polymer Journal 39 (2003) 1091–1097
various fluorescent materials with different emission region could be successfully prepared. Therefore, the copolymer of styrene and maleic anhydride containing pendent 1,8-naphthalimide moiety would be promising solid state fluorescent materials. Due to the susceptibility of forming a six-member ring when maleic anhydride was condensed with hydrazine, copoly(SMA) was treated with the amines as the final step. These compounds have not only made the polymer fluorescent, but also made it more stable than SMA. At the same time, we obtained novel red, yellow and green fluorescent materials. These compounds are soluble in many solvents such as toluene, chloroform, tetrahydrofuran, and so on. We found that all of these copolymers have excellent film-forming properties. We also change the styrene percentage in SMA polymer chain to find that the fluorescent intensity of the polymers containing identical functional group was different when the percentage of styrene increased. The fluorescence took on a growing trend with the percentage increase of styrene in SMA.
2. Experimental 1 H-NMR spectroscopy was recorded by Bruker 500 MHz (relative to TMS). Mass spectra were obtained with HP5989A, Mariner API time of flight (TOF, TIS ion source, PE Corp.) and API2000 (TIS, PE Corp.) spectrometers. Infrared spectra were measured on a Nicolet Magna IR550. UV–Vis–NIR spectra were recorded on a Varian Cary500. Fluorescence spectroscopy was recorded on a Varian Cary Eclipse Fluorescence Spectrophotometer. Quinoline was distilled over calcium hydride. The representative syntheses were shown by Schemes 2 and 3. SMA series were donated by SARTOMER Co. Inc. (ATOFINA) Shanghai Office. The GPC data show that the Mn , Mw , and D of SMA polymers are 4:74 103 , 9:25 103 and 1.95 respectively.
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2.2. Synthesis of the compound PSMI4 (n : m ¼ 1 : 6) A mixture of R-PCTM (0.2 g, 0.43 mmol), 0.62 g (0.86 mmol) of SMA6000 (n : m ¼ 1 : 6) and acetate acid (50 ml) was heated under reflux for 30 h. Then 20 ml of acetic anhydrides was added. The mixture was heated under reflux. After stirring for 4 h, the reaction mixture was filtered and the filtrate was removed at reduced pressure and the residue was dried; 0.11 g (yield 76.1%), m.p. ¼ 142–148 °C. 1 H-NMR (500 MHz, DMSO-d6 ) d ¼ 9:02–8.59 (b, perylene-H), 7.50–6.0 (b, benzene-H), 4.09 (t, N–CH2 ), 2.4–1.0 (b, CH, CH2 ). IR (KBr): m ¼ 3250, 3010, 1770, 1700, 1650, 1600, 1480, 700 cm1 . UV–Vis absorption maximum (in toluene): 528.2, 482.2, 461.0 nm. And PSMI1, PSMI2 and PSMI3 were obtained in the same way of obtaining PSMI4. 2.3. Synthesis of 4-dimethylamino-1,8-naphthal anhydride (I) [17] A mixture of 4-bromine-1,8-naphthalic anhydride (4.6 g, 16 mmol), copper (II) sulfate pentahydrate (0.4 g, 1 mmol) and N,N-dimethylformamide (80 ml) was heated under reflux for 4 h, the hot solution was poured into 400 ml of water. The resulting solution was adjusted to pH ¼ 5.5 by hydrochloric acid. The resulting precipitate was filtered, washed by water, dried and crystallized from the mixed solution of chlorobenzene and ethyl alcohol absolute (1:1) to give 2.95 g (I) in 76% yield, m.p. ¼ 206–208 °C. 2.4. Synthesis of N-amino-4-dimethylamino-1,8-naphthalimides (II) [16,17] A mixture of I (2.68 g, 11 mmol), hydrazine hydrate (2 ml, 80%) and ethyl alcohol absolute (110 ml) was stirred at room temperature for 7 h. The end of the reaction was filtered and dried under vacuum to obtain 2.53 g (II) in 90% yield, m.p. ¼ 172–174 °C). MS (EI ¼ 70 eV), m=z (%): 255 (100).
2.1. Synthesis of the compound R-PTCM A mixture of R-PCTA (0.8 g, 1.79 mmol), hydrazine hydrate (15 ml) and anhydrous quinoline (50 ml) was stirred and heated at 90 °C under an argon atmosphere, for 8 h, then 100 ml of methanol was added. The reaction mixture was heated at 60 °C for 1 h, then filtered. The residue was washed by methanol. A red power was obtained to give 0.8 g in yield 96%, m:p: > 250 °C, IR (KBr): m ¼ 3340, 3060, 1690, 1660, 1590, 1510, 1480, 1350, 1250, 810, 750 cm1 . 1 H-NMR (500 MHz, CDCl3 ) d ¼ 9:73–9.85 (m, 8H, perylene-H), 5.25 (s, 2H, N– CH2 ), 2.61 (t, 2H, CH2 ), 2.25 (t, 2H, CH2 ), 1.75 (s, 3H, CH3 ). Element analysis: Cal. for C28 H20 N3 O4 , C 72.73, H 4.33, N 9.09, Found: C 72.62, H 4.30, N 9.17%.
2.5. Synthesis of the compound of NDSMI1 (n : m ¼ 1 : 1) The mixture of II (1 g, 4 mmol), SMA1000 (n : m ¼ 1 : 1) (0.8 g, 4 mmol) and acetate acid (30 ml) was heated under reflux for 24 h. Then 5 ml of acetic anhydrides was added. And the mixture was heated under reflux, for 1 h. The reaction mixture was cooled and filtered. The filtered solution was poured into 300 ml of water. The precipitate was filtered and dried in a vacuum to obtain a yellow solid. Then the solid was washed by alcohol at 65 °C until the UV absorption of the compound can not be testified in the alcohol. Then the solid was dried under vacuum to obtain 1 g (NDSMI1) in 58% yield. And
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NDSMI2, NDSMI3 and NDSMI4 were obtained in the same way of obtaining NDSMI1. 2.6. Synthesis of N-amino-4-bromine-1,8-naphthalimides (III) [16,17] A mixture of 4-bromine-1,8-naphthalic anhydride (1 g, 3.6 mmol), hydrazine hydrate (1 ml, 80%) and ethyl alcohol absolute (30 ml) was stirred at room temperature for 7 h. The end of the reaction was filtered and dried under vacuum and crystallized from chlorobenzene to give 0.91 g (II) in 91% yield, m.p. ¼ 218–220 °C. MS (EI ¼ 70 eV), m=z (%): 290 (100); 292 (98.6). 2.7. Synthesis of N-amino-4-hexahydropyridine-1,8-naphthalimides (IV) A mixture of III (3.1 g, 11 mmol), hexahydropyridine (1.2 ml), and ethylene glycol mono-methyl ether (30 ml) was heated under reflux for 3 h, then cooled. The resulting precipitate was filtered and washed by diethyl ether anhydrous and dried. The solid was crystallized from 65% of alcohol solution to give 2.66 g in 82% yield, m.p. ¼ 208–210 °C. MS (EI ¼ 70 eV), m=z (%): 295 (100). 2.8. Synthesis of N-amino-4-morpholine-1,8-naphthalimides (V) A mixture of III (2.2 g, 11 mmol), morpholine (1.2 ml), and ethylene glycol mono-methyl ether (30 ml) was heated under reflux for 3 h, then cooled. The resulting precipitate was filtered and washed by diethyl ether anhydrous and dried. The solid was crystallized from 80% of alcohol solution to give 2.60 g in 80% yield, m.p. ¼ 215–217 °C. MS (EI ¼ 70 eV), m=z (%): 297 (100). 2.9. Synthesis of the compound of NHSMI2 (n : m ¼ 1 : 2) The mixture of IV (0.50 g, 1.7 mmol), SMA2000 (n : m ¼ 1 : 2) (0.52 g, 1.7 mmol) and acetate acid (30 ml) was heated under reflux for 24 h. Then 5 ml of acetic anhydrides was added. And the mixture was heated
under reflux, for 1 h. The reaction mixture was cooled and filtered. The filtered solution was poured into 300 ml of water. The precipitate was filtered and dried in a vacuum to obtain an orange solid. Then the solid was washed by alcohol at 65 °C until the UV absorption of the compound can not be testified in the alcohol. Then the solid was dried under vacuum to obtain 0.5 g (NHSMI2) in 50% yield. And NHSMI1, NHSMI3, NHSMI4 all can be obtained using similar synthetic route of NHSMI2. We found that the Tg of the functional polymers is higher than SMA, the Tg of NHSMI4 is 155 °C, but the Tg of SMA is 133.5 °C. It means that the functional polymers are more stable than SMA. The GPC Mn , Mw , and D of polymers are 4:74 103 , 9:25 103 and 1.95 respectively. 2.10. Synthesis of the compound of NMSMI4 (n : m ¼ 1 : 4) The compound of NMSMI4 was obtained by the same method of the synthesis of the compound of NHSMI2 in 50% yield. IR (KBr) cm1 : 3010, 2910, 1740, 1600, 1495, 1450, 750, 700 cm1 . 1 H NMR (CDCl3 ) ppm: 6.6–6.8 (benzene-H), 1.8–2, 3.6–3.8 (–CH–, –CH2 , morpholine-CH2 ). And NMSMI1, NMSMI2, NMSMI3, NESMI4 and NPSMI4 were all obtained in the same way of obtaining NMSMI4.
3. Results and discussion Table 1 shows the absorption and fluorescence data of PSMI does not change with the percentage of styrene in SMA. The maximum absorptions (kmax ) of the PSMI compounds are the same, so are the fluorescence of the PSMI compounds. But the absorption difference in efficiency is due that they are homologous series compounds having different perylene contents. Fig. 1 shows, compared PSMI in toluene with the solid, the maximum absorptions of PSMI in the film are red shifted. This phenomenon has been commentated by Schnurpfeil [18], who explained that with the accretion of the perylene concentration, the perylene tetracarboxyldiimide com-
Table 1 Absorption and fluorescence data of PSMI polymers Compound PSMI4 PSMI3 PSMI2 PSMI1
In toulene
Film
kabs max (nm)
e (104 M1 cm1 )
kem max (nm)
Ufl (%)
kabs max (nm)
kem max (nm)
528 529 528 528
0.399 0.784 1.61 0.776
582 581 579 579
25.4 50.5 81.0 52.4
534; 535; 536; 542;
637.2 636.1 638.5 546.4
498.5 498 498.5 502.5
Note: The relative fluorescence quantum yield Ufl are performed on excitation at 528 nm with the concentration of 105 M in aerated toluene. Rhodamine 6G is employed as an internal standard and its fluorescence quantum yield is defined as 100%.
C. Li et al. / European Polymer Journal 39 (2003) 1091–1097
Fig. 1. The absorption spectra of PSMI4 in (a) PSMI4 film and (b) toluene.
pound became more aggregative. The maximum absorptions of the state of aggregation would be red shifted, and the fluorescence efficiency will drop down obviously. Fig. 2 shows the fluorescence of PSMI3 in its solid and in toluene. The PSMI4 solid fluorescence efficiency is about 10% of that of the solution, and the maximum fluorescence red shift. The solid fluorescence of PSMI3 is the strongest one, which can be explained by the fact that the perylene rings in PSMI3 are separated to the most extent. Due to the high photostability, broad visible-light absorption and high extinction coefficiency of perylene, they are potentially interesting compounds for solar cells. The photovoltaic properties of PSMI3 blending (2%) in MEH–PPV were shown in Fig. 3 and the maximum photosensitivity was 0.1 mA/W around 530 nm. The optimal all-plastic solar cell devices are being made on the progress. Because that perylene has good stability, the perylene-copolymers shown here have potential application for photoelectric conversion. In fact, the
Fig. 2. Fluorescence spectra of PSMI3 in (a) the solid state and (b) PSMI3 in toluene.
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Fig. 3. The current–voltage curve of PSMI3 blending in MEH– PPV polymer.
good solubility of polymers for the blending photoelectric convert medium could reduce the phase-separation which influences the convert efficiency strongly. In addition, since perylene derivatives have good match with the energy band of some semiconductor, these new perylene copolymers with good solubility could be developed further as the sensitizer. Table 2 shows that the absorption maximum wavelength of NHSMI is the longest, and that of NDSMI is the shortest. This is due to the fact that the conjugation systems of NHSMI, NPSMI and NMSMI reduce successively, the electron donating ability of oxygen atom is weaker than that of N atom and C atom for the electron negativity of C, N, O is in an increasing trend. These copolymers have strong fluorescence in solid state. The fluorescence intensity of NDSMI is weaker than that of NMSMI, NHSMI, NESMI and NPSMI. It can be explained by the fact that the dimethyl in dimethylamino rotates around –C–N– bond, through this way it absorbs the most part of energy it gains, which leads to the decrease of the fluorescence. We found that the color of the polymers becomes deeper with the ratio of n : m increasing. For example, the color of NMSMI4, NMSMI3, NMSMI2, NMSMI is dark orange, orange, green, and light yellow respectively. But we also found that the intensity of the polymers fluorescence in tetrahydrofuran increases first and then decreases with the concentration decreasing. Fig. 4 shows the fluorescence of compound NMSMI in tetrahydrofuran. The fluorescent intensity of NMSMI2 is the largest and that of NMSMI1 is the smallest. It is because that when the concentration is high, the fluorescence intensity of polymers is decided by the distraction degree, but when the concentration is low, the fluorescence intensity of polymers is decided by the concentration of the fluorescent groups. Fig. 5 shows the fluorescence of compound NMSMI film is almost identical with that in tetrahydrofuran.
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Table 2 Absorption and fluorescence data of the copolymers Polymer
In THF kabs max
NDSMI1 NDSMI2 NDSMI3 NDSMI4 NMSMI1 NMSMI2 NMSMI3 NMSMI4 NESMI4 NPSMI4
(nm)
341.2 342.0 341.6 341.2 400.2 392.8 401.2 400.6 339.8 396.5
4
1
e (10 M 1.287 1.290 1.328 1.300 1.050 1.049 1.076 1.075 1.382
1
cm )
kem max
(nm)
505 511 511 512 522 512 518 516 450 450
fl
U (%) 55.2 69.5 77.4 49.6
61.9
Film kem max (nm)
Actual value
Calculate value
540 544 540 539 547 544 529 530 518 498
45.98 26.15 10.44 8.18 32.57 43.31 7.6 6.16 2.70 8.4
55.80 45.45 33.16 21.10 59.52 49.25 36.62 29.15 39.83 27.9
546 546
46.95 27.67 25.02 8.38
59.36 49.08 36.46 27.16
Fluorophore weight percentage (%)
In chloroform NHSMI1 NHSMI2 NHSMI3 NHSMI4
423.0 421.4 421.6 421.6
0.742 0.701 0.746 0.762
520 519
Note: The relative fluorescence quantum yield Ufl are relative to Rhodamine 6G standard (defined as 100%).
4. Conclusion
Fig. 4. Fluorescence of NMSMI in tetrahydrofuran (excited by 402 nm).
We have synthesized novel fluorescent SMA copolymers with high quantum yield based on the modified 3,4,9,10-perylenetetracarboxylic mono-anhydride mono-imide and 1,8-naphthalimide derivatives. These novel SMA copolymers are more stable than SMA, which can be proved by the increasing of Tg of them. It is also found that the content of styrene in SMA influenced the fluorescent quantum yield of copolymers which increased first and then decreased. All SMA copolymers synthesized herein show solid state fluorescence emission, which would be very promising functional materials for various applications.
Acknowledgements This work is supported by BASF AG/Germany, NSFC/China and Shanghai Education Committee. Authors thank Prof. Cao Y (South China University of Science and Technology) for the photovoltaic measurements, and thank Dr. P. Erk in BASF for the helpful discussion. C. Hua is now in Sartomer Co. Inc. (ATOFINA) Shanghai Office.
References
Fig. 5. Fluorescence of compound NMSMI film.
[1] Divya C, Marianna K, Dimitris V, Hatzikiriakos Savvas G. Rheol Acta 2002;41:10–24. [2] Lee Yoon C. Monsanto Co., USA, US 4136135. [3] Lee S-s, Ahn TO. J Appl Polym Sci 1999;71:1187–96.
C. Li et al. / European Polymer Journal 39 (2003) 1091–1097 [4] Vermeesch I, Groeninckx G. J Appl Polym Sci 1994;53: 1365–73. [5] Davidson G, Soutar I, Preston PN, Shah VK, Simpson SW, Stewart NJ. Polymer 1994;35:653–7. [6] Tr€ oster H. Dyes Pigments 1983;4:171–7. [7] Yudinori N. Chem Lett 1979:151–2. [8] van der Boom T, Hayes RT, Zhao Y, Bushard PJ, Weiss EA, Wasielewski MR. J Am Chem Soc 2002;124:9582–3. [9] Quante H, Geerts Y, M€ ullen K. Chem Mater 1997;9:495– 500. [10] Seybold G, Wagenblast G. Dyes Pigments 1989;11:303–17. [11] (a) Ferrere S, Zaban A, Gregg BA. J Phys Chem B 1997;101:4490–5;
[12] [13] [14] [15] [16] [17] [18]
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(b) Tian H, Liu PH, Zhu WH, Gao E, Wu DJ, Cai SM. J Mater Chem 2000;10:2708–15. W€ urthner F, Thalacker C, Sutter A. Adv Mater 1999;11: 754–8. Utsugi K, Takano S. J Electrochem Soc 1992;12:3610–5. Cacialli F, Friend RH, Bouche C-M, Le Barny P, Facoetti H, Soyer F. J Appl Phys 1998;83:2343–56. Zhu WH, Hu C, Tian H. Synth Met 1998;96:151–4. Tian H, Xu T, Zhao YB, Chen KC. J Chem Soc Perkin Trans 1999;2:545–9. Xu T, Su JH, Chen KC, Tian H. Heterocycl Commun 1999;5:31–6. Schnurpfeil G. Dyes Pigments 1995;27:339–45.
Synthesis of novel copoly(styrene–maleic anhydride) materials and their luminescent properties Chen Li, Xingang Pan, Chunfan Hua, Jianhua Su, He Tian
*
Institute of Fine Chemicals, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China Received 19 September 2002; received in revised form 14 November 2002; accepted 15 November 2002
Abstract Two series of new high fluorescent polymeric materials based on copoly(styrene–maleic anhydride) (SMA) were prepared by the condensation of SMA with fluorescent groups. One series consists of 1,8-naphthalimides derivatives that are linked with SMA. The other series were prepared by the condensation of SMA with 3,4,9,10-perylene tetracarboxylic mono-anhydride mono-imide. These simple routes to copolymer of styrene and maleic anhydride containing pendent luminescent moiety are promising in increasing fluorescent quantum yield in solid state and processing, in which styrene is employed as ‘‘diluents’’. The luminescent and the preliminary photovoltaic properties of these copolymers have been investigated. Ó 2003 Elsevier Science Ltd. All rights reserved. Keywords: Copolymer; Synthesis; Fluorescence; Perylene; 1,8-Naphthalimide
1. Introduction Polymer blending is widely used as a cost-effective way of producing new materials with customized properties. As polymer blends represent more than 30% of all plastics sold today and are amongst the most rapidly growing areas of polymer technology [1]. The copoly(styrene–maleic anhydride) (SMA) is a kind of polymer materials for commercial use. Lee et al. [2,3] first obtained it in 1979. Vermeesch [4] obtained chemical modified SMA with primary N-alkylamines by reactive extrusion. Because of its good properties and low cost, SMA is widely used in various areas such as automobile materials, electronic household applications etc. In recent years, because SMA can react easily with other compounds which have unique properties, many novel functional materials with the copoly(SMA) have emerged. And there is a widespread interest in polymeric luminescent materials, especially from the viewpoint of
*
Corresponding author. Tel./fax: +86-21-64252288. E-mail address: [email protected] (H. Tian).
excellent film-forming property and good solubility, which makes processing easier by simple spin coating. Meanwhile, to reduce the crystal density and lattice energy and increase the fluorescent quantum yield, many efforts have been made to incorporate the luminescent moiety into copolymers [5,6]. In this way, the chance of fluorescent quenching could be decreased as effort. Therefore, the copolymer of styrene and maleic anhydride containing pendent luminescent moiety would be promising in increasing fluorescent efficiency and processing, in which styrene is employed as ‘‘diluent’’ [7]. In this paper, we describe two approaches to get new fluorescent SMA polymeric materials with high quantum yield. The target compounds are shown in Scheme 1. In the first approach shown in Scheme 2, 3,4,9,10perylene tetracarboxylic mono-anhydride mono-imide [8–10] was condensed with hydrazine. The unsymmetrical perylene tetracarboxydiimide polymers were prepared by the condensation of the mono-imide intermediate with copoly(SMA). Dyes based on perylene 3,4,9,10-tetracarboxylic bisimides (PTCAs) draw much attention recently for used as the sensitizers of nanocrystalline semiconductors solar cells (Gr€ atzel type) with
0014-3057/03/$ - see front matter Ó 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0014-3057(02)00361-0
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Scheme 1. The molecular structures of novel fluorescent polymers.
O
O
N
O
O
O
O
O
N
NNH2
CoPoly(SMA)
NH2 NH2
O
R-PTCA
PSMIx
O
R-PTCM Scheme 2. Synthetic scheme of PSMI.
their outstanding chemical, thermal and photochemical stability [11,12]. PTCAs are highly absorbing in the visible to NIR (e 105 M1 cm1 ) and emit fluorescence with quantum yield near unity. It is crucially important for solar cell sensitizers to control the valence band since most of inorganic semiconductors such as SnO2 exhibit n-type character. A simple approach was to utilize two or more different dyes by a doping method, which show strong absorption at different wavelength and compensate absorbency. We used assembling idea and have explored some multi-chromophoric perylene compounds to extend the sensitizing spectral region with the maximum IPCE up to 24% [11b]. The results told us that perylene derivatives have good energy match with the
O
O
O
NH2NH2 R
O
energy band of SnO2 semiconductor. Therefore, some new perylene copolymers with good solubility have been developed here further and would be expected to be used for all-plastic solar cells application. The second approach (shown in Scheme 3) was based on 1,8-naphthalimide instead of 3,4,9,10-perylene tetracarboxylic mono-anhydride mono-imide. Naphthalimide derivatives have been widely used as brilliant fluorescent dyes in synthetic fiber technology and as electroluminescent materials [13–15]. The color including emission color of 1,8-naphthalimides can be tuned by substitution on the 4-position of the naphthalimide ring [16,17]. When suitable substituents were linked with spacers on the 4-position of the naphthalimide ring,
H2NN
CoPoly(SMA) R
O
NHSMIx NPSMIx NMSMIx NDSMIx NESMIx
Scheme 3. Synthetic scheme of NHSMI, NPSMI, NMSMI, NDSMI and NESMI.
C. Li et al. / European Polymer Journal 39 (2003) 1091–1097
various fluorescent materials with different emission region could be successfully prepared. Therefore, the copolymer of styrene and maleic anhydride containing pendent 1,8-naphthalimide moiety would be promising solid state fluorescent materials. Due to the susceptibility of forming a six-member ring when maleic anhydride was condensed with hydrazine, copoly(SMA) was treated with the amines as the final step. These compounds have not only made the polymer fluorescent, but also made it more stable than SMA. At the same time, we obtained novel red, yellow and green fluorescent materials. These compounds are soluble in many solvents such as toluene, chloroform, tetrahydrofuran, and so on. We found that all of these copolymers have excellent film-forming properties. We also change the styrene percentage in SMA polymer chain to find that the fluorescent intensity of the polymers containing identical functional group was different when the percentage of styrene increased. The fluorescence took on a growing trend with the percentage increase of styrene in SMA.
2. Experimental 1 H-NMR spectroscopy was recorded by Bruker 500 MHz (relative to TMS). Mass spectra were obtained with HP5989A, Mariner API time of flight (TOF, TIS ion source, PE Corp.) and API2000 (TIS, PE Corp.) spectrometers. Infrared spectra were measured on a Nicolet Magna IR550. UV–Vis–NIR spectra were recorded on a Varian Cary500. Fluorescence spectroscopy was recorded on a Varian Cary Eclipse Fluorescence Spectrophotometer. Quinoline was distilled over calcium hydride. The representative syntheses were shown by Schemes 2 and 3. SMA series were donated by SARTOMER Co. Inc. (ATOFINA) Shanghai Office. The GPC data show that the Mn , Mw , and D of SMA polymers are 4:74 103 , 9:25 103 and 1.95 respectively.
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2.2. Synthesis of the compound PSMI4 (n : m ¼ 1 : 6) A mixture of R-PCTM (0.2 g, 0.43 mmol), 0.62 g (0.86 mmol) of SMA6000 (n : m ¼ 1 : 6) and acetate acid (50 ml) was heated under reflux for 30 h. Then 20 ml of acetic anhydrides was added. The mixture was heated under reflux. After stirring for 4 h, the reaction mixture was filtered and the filtrate was removed at reduced pressure and the residue was dried; 0.11 g (yield 76.1%), m.p. ¼ 142–148 °C. 1 H-NMR (500 MHz, DMSO-d6 ) d ¼ 9:02–8.59 (b, perylene-H), 7.50–6.0 (b, benzene-H), 4.09 (t, N–CH2 ), 2.4–1.0 (b, CH, CH2 ). IR (KBr): m ¼ 3250, 3010, 1770, 1700, 1650, 1600, 1480, 700 cm1 . UV–Vis absorption maximum (in toluene): 528.2, 482.2, 461.0 nm. And PSMI1, PSMI2 and PSMI3 were obtained in the same way of obtaining PSMI4. 2.3. Synthesis of 4-dimethylamino-1,8-naphthal anhydride (I) [17] A mixture of 4-bromine-1,8-naphthalic anhydride (4.6 g, 16 mmol), copper (II) sulfate pentahydrate (0.4 g, 1 mmol) and N,N-dimethylformamide (80 ml) was heated under reflux for 4 h, the hot solution was poured into 400 ml of water. The resulting solution was adjusted to pH ¼ 5.5 by hydrochloric acid. The resulting precipitate was filtered, washed by water, dried and crystallized from the mixed solution of chlorobenzene and ethyl alcohol absolute (1:1) to give 2.95 g (I) in 76% yield, m.p. ¼ 206–208 °C. 2.4. Synthesis of N-amino-4-dimethylamino-1,8-naphthalimides (II) [16,17] A mixture of I (2.68 g, 11 mmol), hydrazine hydrate (2 ml, 80%) and ethyl alcohol absolute (110 ml) was stirred at room temperature for 7 h. The end of the reaction was filtered and dried under vacuum to obtain 2.53 g (II) in 90% yield, m.p. ¼ 172–174 °C). MS (EI ¼ 70 eV), m=z (%): 255 (100).
2.1. Synthesis of the compound R-PTCM A mixture of R-PCTA (0.8 g, 1.79 mmol), hydrazine hydrate (15 ml) and anhydrous quinoline (50 ml) was stirred and heated at 90 °C under an argon atmosphere, for 8 h, then 100 ml of methanol was added. The reaction mixture was heated at 60 °C for 1 h, then filtered. The residue was washed by methanol. A red power was obtained to give 0.8 g in yield 96%, m:p: > 250 °C, IR (KBr): m ¼ 3340, 3060, 1690, 1660, 1590, 1510, 1480, 1350, 1250, 810, 750 cm1 . 1 H-NMR (500 MHz, CDCl3 ) d ¼ 9:73–9.85 (m, 8H, perylene-H), 5.25 (s, 2H, N– CH2 ), 2.61 (t, 2H, CH2 ), 2.25 (t, 2H, CH2 ), 1.75 (s, 3H, CH3 ). Element analysis: Cal. for C28 H20 N3 O4 , C 72.73, H 4.33, N 9.09, Found: C 72.62, H 4.30, N 9.17%.
2.5. Synthesis of the compound of NDSMI1 (n : m ¼ 1 : 1) The mixture of II (1 g, 4 mmol), SMA1000 (n : m ¼ 1 : 1) (0.8 g, 4 mmol) and acetate acid (30 ml) was heated under reflux for 24 h. Then 5 ml of acetic anhydrides was added. And the mixture was heated under reflux, for 1 h. The reaction mixture was cooled and filtered. The filtered solution was poured into 300 ml of water. The precipitate was filtered and dried in a vacuum to obtain a yellow solid. Then the solid was washed by alcohol at 65 °C until the UV absorption of the compound can not be testified in the alcohol. Then the solid was dried under vacuum to obtain 1 g (NDSMI1) in 58% yield. And
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NDSMI2, NDSMI3 and NDSMI4 were obtained in the same way of obtaining NDSMI1. 2.6. Synthesis of N-amino-4-bromine-1,8-naphthalimides (III) [16,17] A mixture of 4-bromine-1,8-naphthalic anhydride (1 g, 3.6 mmol), hydrazine hydrate (1 ml, 80%) and ethyl alcohol absolute (30 ml) was stirred at room temperature for 7 h. The end of the reaction was filtered and dried under vacuum and crystallized from chlorobenzene to give 0.91 g (II) in 91% yield, m.p. ¼ 218–220 °C. MS (EI ¼ 70 eV), m=z (%): 290 (100); 292 (98.6). 2.7. Synthesis of N-amino-4-hexahydropyridine-1,8-naphthalimides (IV) A mixture of III (3.1 g, 11 mmol), hexahydropyridine (1.2 ml), and ethylene glycol mono-methyl ether (30 ml) was heated under reflux for 3 h, then cooled. The resulting precipitate was filtered and washed by diethyl ether anhydrous and dried. The solid was crystallized from 65% of alcohol solution to give 2.66 g in 82% yield, m.p. ¼ 208–210 °C. MS (EI ¼ 70 eV), m=z (%): 295 (100). 2.8. Synthesis of N-amino-4-morpholine-1,8-naphthalimides (V) A mixture of III (2.2 g, 11 mmol), morpholine (1.2 ml), and ethylene glycol mono-methyl ether (30 ml) was heated under reflux for 3 h, then cooled. The resulting precipitate was filtered and washed by diethyl ether anhydrous and dried. The solid was crystallized from 80% of alcohol solution to give 2.60 g in 80% yield, m.p. ¼ 215–217 °C. MS (EI ¼ 70 eV), m=z (%): 297 (100). 2.9. Synthesis of the compound of NHSMI2 (n : m ¼ 1 : 2) The mixture of IV (0.50 g, 1.7 mmol), SMA2000 (n : m ¼ 1 : 2) (0.52 g, 1.7 mmol) and acetate acid (30 ml) was heated under reflux for 24 h. Then 5 ml of acetic anhydrides was added. And the mixture was heated
under reflux, for 1 h. The reaction mixture was cooled and filtered. The filtered solution was poured into 300 ml of water. The precipitate was filtered and dried in a vacuum to obtain an orange solid. Then the solid was washed by alcohol at 65 °C until the UV absorption of the compound can not be testified in the alcohol. Then the solid was dried under vacuum to obtain 0.5 g (NHSMI2) in 50% yield. And NHSMI1, NHSMI3, NHSMI4 all can be obtained using similar synthetic route of NHSMI2. We found that the Tg of the functional polymers is higher than SMA, the Tg of NHSMI4 is 155 °C, but the Tg of SMA is 133.5 °C. It means that the functional polymers are more stable than SMA. The GPC Mn , Mw , and D of polymers are 4:74 103 , 9:25 103 and 1.95 respectively. 2.10. Synthesis of the compound of NMSMI4 (n : m ¼ 1 : 4) The compound of NMSMI4 was obtained by the same method of the synthesis of the compound of NHSMI2 in 50% yield. IR (KBr) cm1 : 3010, 2910, 1740, 1600, 1495, 1450, 750, 700 cm1 . 1 H NMR (CDCl3 ) ppm: 6.6–6.8 (benzene-H), 1.8–2, 3.6–3.8 (–CH–, –CH2 , morpholine-CH2 ). And NMSMI1, NMSMI2, NMSMI3, NESMI4 and NPSMI4 were all obtained in the same way of obtaining NMSMI4.
3. Results and discussion Table 1 shows the absorption and fluorescence data of PSMI does not change with the percentage of styrene in SMA. The maximum absorptions (kmax ) of the PSMI compounds are the same, so are the fluorescence of the PSMI compounds. But the absorption difference in efficiency is due that they are homologous series compounds having different perylene contents. Fig. 1 shows, compared PSMI in toluene with the solid, the maximum absorptions of PSMI in the film are red shifted. This phenomenon has been commentated by Schnurpfeil [18], who explained that with the accretion of the perylene concentration, the perylene tetracarboxyldiimide com-
Table 1 Absorption and fluorescence data of PSMI polymers Compound PSMI4 PSMI3 PSMI2 PSMI1
In toulene
Film
kabs max (nm)
e (104 M1 cm1 )
kem max (nm)
Ufl (%)
kabs max (nm)
kem max (nm)
528 529 528 528
0.399 0.784 1.61 0.776
582 581 579 579
25.4 50.5 81.0 52.4
534; 535; 536; 542;
637.2 636.1 638.5 546.4
498.5 498 498.5 502.5
Note: The relative fluorescence quantum yield Ufl are performed on excitation at 528 nm with the concentration of 105 M in aerated toluene. Rhodamine 6G is employed as an internal standard and its fluorescence quantum yield is defined as 100%.
C. Li et al. / European Polymer Journal 39 (2003) 1091–1097
Fig. 1. The absorption spectra of PSMI4 in (a) PSMI4 film and (b) toluene.
pound became more aggregative. The maximum absorptions of the state of aggregation would be red shifted, and the fluorescence efficiency will drop down obviously. Fig. 2 shows the fluorescence of PSMI3 in its solid and in toluene. The PSMI4 solid fluorescence efficiency is about 10% of that of the solution, and the maximum fluorescence red shift. The solid fluorescence of PSMI3 is the strongest one, which can be explained by the fact that the perylene rings in PSMI3 are separated to the most extent. Due to the high photostability, broad visible-light absorption and high extinction coefficiency of perylene, they are potentially interesting compounds for solar cells. The photovoltaic properties of PSMI3 blending (2%) in MEH–PPV were shown in Fig. 3 and the maximum photosensitivity was 0.1 mA/W around 530 nm. The optimal all-plastic solar cell devices are being made on the progress. Because that perylene has good stability, the perylene-copolymers shown here have potential application for photoelectric conversion. In fact, the
Fig. 2. Fluorescence spectra of PSMI3 in (a) the solid state and (b) PSMI3 in toluene.
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Fig. 3. The current–voltage curve of PSMI3 blending in MEH– PPV polymer.
good solubility of polymers for the blending photoelectric convert medium could reduce the phase-separation which influences the convert efficiency strongly. In addition, since perylene derivatives have good match with the energy band of some semiconductor, these new perylene copolymers with good solubility could be developed further as the sensitizer. Table 2 shows that the absorption maximum wavelength of NHSMI is the longest, and that of NDSMI is the shortest. This is due to the fact that the conjugation systems of NHSMI, NPSMI and NMSMI reduce successively, the electron donating ability of oxygen atom is weaker than that of N atom and C atom for the electron negativity of C, N, O is in an increasing trend. These copolymers have strong fluorescence in solid state. The fluorescence intensity of NDSMI is weaker than that of NMSMI, NHSMI, NESMI and NPSMI. It can be explained by the fact that the dimethyl in dimethylamino rotates around –C–N– bond, through this way it absorbs the most part of energy it gains, which leads to the decrease of the fluorescence. We found that the color of the polymers becomes deeper with the ratio of n : m increasing. For example, the color of NMSMI4, NMSMI3, NMSMI2, NMSMI is dark orange, orange, green, and light yellow respectively. But we also found that the intensity of the polymers fluorescence in tetrahydrofuran increases first and then decreases with the concentration decreasing. Fig. 4 shows the fluorescence of compound NMSMI in tetrahydrofuran. The fluorescent intensity of NMSMI2 is the largest and that of NMSMI1 is the smallest. It is because that when the concentration is high, the fluorescence intensity of polymers is decided by the distraction degree, but when the concentration is low, the fluorescence intensity of polymers is decided by the concentration of the fluorescent groups. Fig. 5 shows the fluorescence of compound NMSMI film is almost identical with that in tetrahydrofuran.
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Table 2 Absorption and fluorescence data of the copolymers Polymer
In THF kabs max
NDSMI1 NDSMI2 NDSMI3 NDSMI4 NMSMI1 NMSMI2 NMSMI3 NMSMI4 NESMI4 NPSMI4
(nm)
341.2 342.0 341.6 341.2 400.2 392.8 401.2 400.6 339.8 396.5
4
1
e (10 M 1.287 1.290 1.328 1.300 1.050 1.049 1.076 1.075 1.382
1
cm )
kem max
(nm)
505 511 511 512 522 512 518 516 450 450
fl
U (%) 55.2 69.5 77.4 49.6
61.9
Film kem max (nm)
Actual value
Calculate value
540 544 540 539 547 544 529 530 518 498
45.98 26.15 10.44 8.18 32.57 43.31 7.6 6.16 2.70 8.4
55.80 45.45 33.16 21.10 59.52 49.25 36.62 29.15 39.83 27.9
546 546
46.95 27.67 25.02 8.38
59.36 49.08 36.46 27.16
Fluorophore weight percentage (%)
In chloroform NHSMI1 NHSMI2 NHSMI3 NHSMI4
423.0 421.4 421.6 421.6
0.742 0.701 0.746 0.762
520 519
Note: The relative fluorescence quantum yield Ufl are relative to Rhodamine 6G standard (defined as 100%).
4. Conclusion
Fig. 4. Fluorescence of NMSMI in tetrahydrofuran (excited by 402 nm).
We have synthesized novel fluorescent SMA copolymers with high quantum yield based on the modified 3,4,9,10-perylenetetracarboxylic mono-anhydride mono-imide and 1,8-naphthalimide derivatives. These novel SMA copolymers are more stable than SMA, which can be proved by the increasing of Tg of them. It is also found that the content of styrene in SMA influenced the fluorescent quantum yield of copolymers which increased first and then decreased. All SMA copolymers synthesized herein show solid state fluorescence emission, which would be very promising functional materials for various applications.
Acknowledgements This work is supported by BASF AG/Germany, NSFC/China and Shanghai Education Committee. Authors thank Prof. Cao Y (South China University of Science and Technology) for the photovoltaic measurements, and thank Dr. P. Erk in BASF for the helpful discussion. C. Hua is now in Sartomer Co. Inc. (ATOFINA) Shanghai Office.
References
Fig. 5. Fluorescence of compound NMSMI film.
[1] Divya C, Marianna K, Dimitris V, Hatzikiriakos Savvas G. Rheol Acta 2002;41:10–24. [2] Lee Yoon C. Monsanto Co., USA, US 4136135. [3] Lee S-s, Ahn TO. J Appl Polym Sci 1999;71:1187–96.
C. Li et al. / European Polymer Journal 39 (2003) 1091–1097 [4] Vermeesch I, Groeninckx G. J Appl Polym Sci 1994;53: 1365–73. [5] Davidson G, Soutar I, Preston PN, Shah VK, Simpson SW, Stewart NJ. Polymer 1994;35:653–7. [6] Tr€ oster H. Dyes Pigments 1983;4:171–7. [7] Yudinori N. Chem Lett 1979:151–2. [8] van der Boom T, Hayes RT, Zhao Y, Bushard PJ, Weiss EA, Wasielewski MR. J Am Chem Soc 2002;124:9582–3. [9] Quante H, Geerts Y, M€ ullen K. Chem Mater 1997;9:495– 500. [10] Seybold G, Wagenblast G. Dyes Pigments 1989;11:303–17. [11] (a) Ferrere S, Zaban A, Gregg BA. J Phys Chem B 1997;101:4490–5;
[12] [13] [14] [15] [16] [17] [18]
1097
(b) Tian H, Liu PH, Zhu WH, Gao E, Wu DJ, Cai SM. J Mater Chem 2000;10:2708–15. W€ urthner F, Thalacker C, Sutter A. Adv Mater 1999;11: 754–8. Utsugi K, Takano S. J Electrochem Soc 1992;12:3610–5. Cacialli F, Friend RH, Bouche C-M, Le Barny P, Facoetti H, Soyer F. J Appl Phys 1998;83:2343–56. Zhu WH, Hu C, Tian H. Synth Met 1998;96:151–4. Tian H, Xu T, Zhao YB, Chen KC. J Chem Soc Perkin Trans 1999;2:545–9. Xu T, Su JH, Chen KC, Tian H. Heterocycl Commun 1999;5:31–6. Schnurpfeil G. Dyes Pigments 1995;27:339–45.