- Email: [email protected]
Novel hyperbranched polyimides from 2,6,12-triaminotriptycene
Available online at www.sciencedirect.com
Chinese Chemical Letters 19 (2008) 1127–1130 www.elsevier.com/locate/cclet
Novel hyperbranched polyimides from 2,6,12-triaminotriptycene Zhen Xu, Xing Quan Xiong, Lin Cheng * Department of Materials Science & Engineering, Huaqiao University, Quanzhou 362021, China Received 21 March 2008
Abstract The monomer 2,6,12-triaminotriptycene was synthesized and the structure was confirmed by IR and 1H NMR spectra. Hyperbranched polyimides modified with different terminal groups were obtained from precursors, anhydride- and aminoterminated hyperbranched poly(amic acid)s from polymerization of A2 + B3 system. From gel permeation chromatogram (GPC) characterization, representative products had high molecular weight. All polymers had good solubility in CHCl3, DMF and tetrahydrofuran (THF), and performed no detective Tgs in the range of 50–300 8C and high Tds above 455 8C when 5% weight loss. # 2008 Lin Cheng. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. Keywords: Triptycene; Hyperbranched polymer; Polyimides
Hyperbranched polymers have attracted much attention for the unique branching architecture and amounts of terminal groups from the pioneering work by Kim and Webster [1], even more than dendrimers: perfectly branched but limited in large-scale industry production. Kinds of hyperbranched polymers have come forth in recent 20 years: polyphenylenes [2], polyimides [3], and so on. Hyperbranched polyimides (HPIs) combined the hyperbranched architecture identities with advantages of polyimides, moreover, exhibited prospective functionality derived from modification by different terminal groups. Triptycene with D3h symmetry and three-dimensional rigid structure was first synthesized by Bartlett et al. [4]. Macromolecules and supramolecules containing triptycene have hitherto become highlight and performed as potential candidates for functional materials. Swager group synthesized conjugated polymer for TNT sensors [5], bis(phenylethynyl)benzene nematic liquid crystals [6] and high-performance polyesters for interlocking by intermolecular triptycene moieties [7]. Budd reported porous network polymers for hydrogen storage [8]. Besides, novel molecular motors expand the potentiality of unique structure of triptycene [9]. The foregoing ideals were based on the structure stretching from 1,4- or 9,10-position of triptycene framework. Recently, we launched the program in the concept of three-dimensional functionality on the basis of triptycene. Herein, we reported syntheses of novel HPIs with varied terminals by A2 + B3 method and looked into the properties thereof.
* Corresponding author. E-mail address: [email protected] (L. Cheng). 1001-8417/$ – see front matter # 2008 Lin Cheng. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. doi:10.1016/j.cclet.2008.05.039
1128
Z. Xu et al. / Chinese Chemical Letters 19 (2008) 1127–1130
1. Experimental 2,2-Bis[4-(3,4-dicarboxyphenoxy) phenyl] propane dianhydride (BPADA) and phthalic anhydride (PA) were recrystallized from acetic anhydride. DMAc was distilled under reduced pressure before use. All other reagents were analytically pure. FTIR were characterized with KBr pellets on Nicolet Nexus 670 FTIR spectrometer. DSC and TGA were performed on PerkinElmer DSC-7 and TA instrument SDT-2960, respectively. 1H NMR was measured on a Bruker DMX-300 instrument. Gel permeation chromatograms (GPCs) using polystyrene as a standard were obtained on a Waters 2414 instrument with tetrahydrofuran (THF) as an eluent at a flow rate of 1.0 mL/min. 1.1. 2,6,12-Triaminotriptycene 3 (TATP) By nitration of triptycene (1) and separation on silica gel, 2,6,12-trinitrotriptycene (2a) and 2,7,12trinitrotriptycene (2b) yielded in 70 and 7%, respectively. Compound 2a: mp: 179–180 8C [10]. 1H NMR (CDCl3, d ppm): 5.82–5.84 (d-d, 2H), 7.62–7.67 (m, 3H), 8.03–8.07 (m, 3H), 8.32–8.34 (m, 3H). 20 mL H2NNH2H2O was slowly dropped into the suspension consist of 2.5 g 2a, 0.5 g Pd/C and 250 mL ethanol under refluxing. With further reaction for 12 h, the solution was rotary-evaporated to get 3 (1.75 g, yield: 88%). Compound 3: mp: 292–293 8C [10]. 1H NMR (CDCl3, d ppm): 3.40 (s, 6H), 5.01–5.04 (d-d, 2H), 6.21–6.26 (m, 3H), 6.69–6.73 (m, 3H), 7.04–7.07 (m, 3H). IR: 3342, 3340, 1627 and 1479 cm 1. 1.2. Amine-terminated hyperbranched polyimides (AM-HPIs) By method 1 in Scheme 1, 10 mL DMAc containing 1 mmol BPADA was dropped into 10 mL DMAc with 1 mmol TATP in 2 h. During further azeotropic distillation by 10 mL toluene at elevated temperature, about 60 8C, yellow precipitate appeared unfortunately and was filtrated. 1.3. Modified AM-HPIs (Ac-AMHPI and PT-AMHPI) During the preparation of AM-HPI, 0.5 mmol acetic anhydride or PA was punched in with further 5 h stirring to react with excessive terminal amines of poly(amic acid). After chemical cycling in the presence of 1 mL acetic
Scheme 1. Condition and reagent. (a) 0.1 mol/L monomer concentration in DMAc, drop very slowly in 2 h, stirring, N2, room temperature; (b) stirring for 10 h; (c) 10 mL toluene, azeotropic dehydration at elevated temperature; (d) introduce modifier reagents, stirring for 5 h; (e) chemical cyclization in the presence of acetic anhydride and pyridine, 120 8C, 12 h, precipitate in ethanol.
Z. Xu et al. / Chinese Chemical Letters 19 (2008) 1127–1130
1129
anhydride and 0.5 mL pyridine at 120 8C for 12 h, products were obtained as Ac-AMHPI and Ph-AMHPI, respectively, with further refinement. Typical refinement was showed that 10 wt% CHCl3 or THF solution of HPIs was precipitated to methanol and dealt with Soxlet method with methanol for 48 h. In the end, under vacuum, the powders were dried at 100 8C for 24 h. 1.4. Anhydride-terminated hyperbranched polyimide (AN-HPI) Turning to method 2, the resultant was obtained as AN-HPI in the end. 1.5. Modified AN-HPI (AT-ANHPI) In the process of preparing AN-HPI, 0.5 mL freshly distilled aniline was adopted to modify anhydride groups of the poly(amic acid), after chemical imidation and refinement, white powder AT-ANHPI was obtained. 2. Results and discussion In the process of polymerization by A2 + B3 method for HPIs, similar to Fang et al. [3], low monomer concentration in DMAc and intense stirring are necessary to keep lowest local concentration in reaction system, further to avoid gel formation. At the stage of poly(amic acid)s, reagents for modifying terminal anhydride or amino groups were introduced and HPIs with varied terminal groups were prepared at last. The insoluble AM-HPI precipitated in the process, the reason is still in progress. GPC data of Ac-AMHPI and AT-ANHPI, which represent two serials of HPIs, respectively, validate the high molecular weight and reveal differences between the two categories about polydispersity. IR spectra of HPIs show the characteristic absorption band of polyimides around 1780, 1720 and 1370 cm 1, and further absence of band around 1680 cm 1, which identified poly(amic acid), confirmed completely imidization. The 1H NMR spectrum (Fig. 1) of Ac-AMHPI conveys that the hyperbranched structure have many terminals, with a ratio of acetamide group to dianhydride moiety in skeleton averaging to 0.85, deduced from integration ratio of a, b marked proton. The multi split peaks ranged from 5.5 to 5.8 ppm were assigned to protons of 9,10- positions in triptycene moiety. It has potential to deduced the degree of branching (DB) of hyperbranched PI, which is the characteristic parameter to hyperbranched architecture. In the range of 50–300 8C, all HPIs show no detective Tgs. As shown in Table 1, PT-AMHPI and AT-ANHPI have higher Td (5%) and Td (10%) than the other two HPIs, which illustrate that terminal groups have strong influence on thermal performance. Moreover, different polydispersity and structure induce two distinct categories curves after 600 8C in Fig. 2, the reason behind is still unknown.
Fig. 1. 1H NMR spectrum of Ac-AMHPI.
1130
Z. Xu et al. / Chinese Chemical Letters 19 (2008) 1127–1130
Table 1 Syntheses and properties of prepared hyperbranched polyimides Entry
Ac-AMHPI PT-AMHPI AN-HPI AT-ANHPI
a
T d5 (8C)
455 530 467 533
b
T d10 (8C)
524 551 525 544
++: soluble at room temperatures; +: soluble at heating; the rate of 10 8C/min after annealing at 300 8C. a 5 wt% weight loss temperatures. b 10 wt% weight loss temperatures.
Mn
9,056 – – 12,194
Mw/Mn
2.48 – – 5.26
Solvents CHCl3
DMF/DMAC
THF
++ + + ++
++ ++ ++ ++
++ + + ++
Acetone
: insoluble at heating; the glass-transition temperatures was determinate under N2 and at
Fig. 2. TGA curves of HPIs.
All HPIs have good solubility in DMF, DMAc and NMP, even in THF and CHCl3, except that PT-AMHPI and ANHPI are soluble when heated in THF and CHCl3. Additionally, the serial of higher Mw/Mn have better solubility approved by comparing PT-AMHPI with AT-ANHPI in THF/CHCl3. In summary, HPIs with different terminal groups were synthesized by A2 + B3 method and performed good solubility and excellent thermal properties. Two factors, terminal groups and hyperbranched structure, impact important influence on the performance of the resultant HPIs and further research is in progress. Acknowledgments The program was financially supported from the National Natural Science Foundation (No. 50673031) of China and authors would like to extend thanks to Professor Yongming Chen at CAS. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]
Y.H. Kim, O.W. Webster, J. Am. Chem. Soc. 112 (1990) 4592. Y.M. Kim, R. Beckerbauer, Macromolecules 27 (1994) 1968. J.H. Fang, H. Kits, K. Okamoto, Macromolecules 33 (2000) 4639. P.D. Bartlett, M.J. Ryan, S.G. Cohen, J. Am. Chem. Soc. 64 (1942) 2649. D.T. Mcquade, T.M. Swager, Chem. Rev. 100 (2000) 2537. T.M. Long, T.M. Swager, J. Mater. Chem. 13 (2002) 3407. N.T. Tsui, A.J. Paraskos, L. Torun, et al. Macromolecules 39 (2006) 3350. B.S. Ghanem, K.J. Msayib, N.B. Mckeown, et al. Chem. Commun. (2007) 67. T.R. Kelly, X. Cai, F. Damkaci, et al. J. Am. Chem. Soc. 129 (2007) 376. Z. Chun, C.F. Chen., J. Org. Chem. 71 (2006) 6626.
Chinese Chemical Letters 19 (2008) 1127–1130 www.elsevier.com/locate/cclet
Novel hyperbranched polyimides from 2,6,12-triaminotriptycene Zhen Xu, Xing Quan Xiong, Lin Cheng * Department of Materials Science & Engineering, Huaqiao University, Quanzhou 362021, China Received 21 March 2008
Abstract The monomer 2,6,12-triaminotriptycene was synthesized and the structure was confirmed by IR and 1H NMR spectra. Hyperbranched polyimides modified with different terminal groups were obtained from precursors, anhydride- and aminoterminated hyperbranched poly(amic acid)s from polymerization of A2 + B3 system. From gel permeation chromatogram (GPC) characterization, representative products had high molecular weight. All polymers had good solubility in CHCl3, DMF and tetrahydrofuran (THF), and performed no detective Tgs in the range of 50–300 8C and high Tds above 455 8C when 5% weight loss. # 2008 Lin Cheng. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. Keywords: Triptycene; Hyperbranched polymer; Polyimides
Hyperbranched polymers have attracted much attention for the unique branching architecture and amounts of terminal groups from the pioneering work by Kim and Webster [1], even more than dendrimers: perfectly branched but limited in large-scale industry production. Kinds of hyperbranched polymers have come forth in recent 20 years: polyphenylenes [2], polyimides [3], and so on. Hyperbranched polyimides (HPIs) combined the hyperbranched architecture identities with advantages of polyimides, moreover, exhibited prospective functionality derived from modification by different terminal groups. Triptycene with D3h symmetry and three-dimensional rigid structure was first synthesized by Bartlett et al. [4]. Macromolecules and supramolecules containing triptycene have hitherto become highlight and performed as potential candidates for functional materials. Swager group synthesized conjugated polymer for TNT sensors [5], bis(phenylethynyl)benzene nematic liquid crystals [6] and high-performance polyesters for interlocking by intermolecular triptycene moieties [7]. Budd reported porous network polymers for hydrogen storage [8]. Besides, novel molecular motors expand the potentiality of unique structure of triptycene [9]. The foregoing ideals were based on the structure stretching from 1,4- or 9,10-position of triptycene framework. Recently, we launched the program in the concept of three-dimensional functionality on the basis of triptycene. Herein, we reported syntheses of novel HPIs with varied terminals by A2 + B3 method and looked into the properties thereof.
* Corresponding author. E-mail address: [email protected] (L. Cheng). 1001-8417/$ – see front matter # 2008 Lin Cheng. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. doi:10.1016/j.cclet.2008.05.039
1128
Z. Xu et al. / Chinese Chemical Letters 19 (2008) 1127–1130
1. Experimental 2,2-Bis[4-(3,4-dicarboxyphenoxy) phenyl] propane dianhydride (BPADA) and phthalic anhydride (PA) were recrystallized from acetic anhydride. DMAc was distilled under reduced pressure before use. All other reagents were analytically pure. FTIR were characterized with KBr pellets on Nicolet Nexus 670 FTIR spectrometer. DSC and TGA were performed on PerkinElmer DSC-7 and TA instrument SDT-2960, respectively. 1H NMR was measured on a Bruker DMX-300 instrument. Gel permeation chromatograms (GPCs) using polystyrene as a standard were obtained on a Waters 2414 instrument with tetrahydrofuran (THF) as an eluent at a flow rate of 1.0 mL/min. 1.1. 2,6,12-Triaminotriptycene 3 (TATP) By nitration of triptycene (1) and separation on silica gel, 2,6,12-trinitrotriptycene (2a) and 2,7,12trinitrotriptycene (2b) yielded in 70 and 7%, respectively. Compound 2a: mp: 179–180 8C [10]. 1H NMR (CDCl3, d ppm): 5.82–5.84 (d-d, 2H), 7.62–7.67 (m, 3H), 8.03–8.07 (m, 3H), 8.32–8.34 (m, 3H). 20 mL H2NNH2H2O was slowly dropped into the suspension consist of 2.5 g 2a, 0.5 g Pd/C and 250 mL ethanol under refluxing. With further reaction for 12 h, the solution was rotary-evaporated to get 3 (1.75 g, yield: 88%). Compound 3: mp: 292–293 8C [10]. 1H NMR (CDCl3, d ppm): 3.40 (s, 6H), 5.01–5.04 (d-d, 2H), 6.21–6.26 (m, 3H), 6.69–6.73 (m, 3H), 7.04–7.07 (m, 3H). IR: 3342, 3340, 1627 and 1479 cm 1. 1.2. Amine-terminated hyperbranched polyimides (AM-HPIs) By method 1 in Scheme 1, 10 mL DMAc containing 1 mmol BPADA was dropped into 10 mL DMAc with 1 mmol TATP in 2 h. During further azeotropic distillation by 10 mL toluene at elevated temperature, about 60 8C, yellow precipitate appeared unfortunately and was filtrated. 1.3. Modified AM-HPIs (Ac-AMHPI and PT-AMHPI) During the preparation of AM-HPI, 0.5 mmol acetic anhydride or PA was punched in with further 5 h stirring to react with excessive terminal amines of poly(amic acid). After chemical cycling in the presence of 1 mL acetic
Scheme 1. Condition and reagent. (a) 0.1 mol/L monomer concentration in DMAc, drop very slowly in 2 h, stirring, N2, room temperature; (b) stirring for 10 h; (c) 10 mL toluene, azeotropic dehydration at elevated temperature; (d) introduce modifier reagents, stirring for 5 h; (e) chemical cyclization in the presence of acetic anhydride and pyridine, 120 8C, 12 h, precipitate in ethanol.
Z. Xu et al. / Chinese Chemical Letters 19 (2008) 1127–1130
1129
anhydride and 0.5 mL pyridine at 120 8C for 12 h, products were obtained as Ac-AMHPI and Ph-AMHPI, respectively, with further refinement. Typical refinement was showed that 10 wt% CHCl3 or THF solution of HPIs was precipitated to methanol and dealt with Soxlet method with methanol for 48 h. In the end, under vacuum, the powders were dried at 100 8C for 24 h. 1.4. Anhydride-terminated hyperbranched polyimide (AN-HPI) Turning to method 2, the resultant was obtained as AN-HPI in the end. 1.5. Modified AN-HPI (AT-ANHPI) In the process of preparing AN-HPI, 0.5 mL freshly distilled aniline was adopted to modify anhydride groups of the poly(amic acid), after chemical imidation and refinement, white powder AT-ANHPI was obtained. 2. Results and discussion In the process of polymerization by A2 + B3 method for HPIs, similar to Fang et al. [3], low monomer concentration in DMAc and intense stirring are necessary to keep lowest local concentration in reaction system, further to avoid gel formation. At the stage of poly(amic acid)s, reagents for modifying terminal anhydride or amino groups were introduced and HPIs with varied terminal groups were prepared at last. The insoluble AM-HPI precipitated in the process, the reason is still in progress. GPC data of Ac-AMHPI and AT-ANHPI, which represent two serials of HPIs, respectively, validate the high molecular weight and reveal differences between the two categories about polydispersity. IR spectra of HPIs show the characteristic absorption band of polyimides around 1780, 1720 and 1370 cm 1, and further absence of band around 1680 cm 1, which identified poly(amic acid), confirmed completely imidization. The 1H NMR spectrum (Fig. 1) of Ac-AMHPI conveys that the hyperbranched structure have many terminals, with a ratio of acetamide group to dianhydride moiety in skeleton averaging to 0.85, deduced from integration ratio of a, b marked proton. The multi split peaks ranged from 5.5 to 5.8 ppm were assigned to protons of 9,10- positions in triptycene moiety. It has potential to deduced the degree of branching (DB) of hyperbranched PI, which is the characteristic parameter to hyperbranched architecture. In the range of 50–300 8C, all HPIs show no detective Tgs. As shown in Table 1, PT-AMHPI and AT-ANHPI have higher Td (5%) and Td (10%) than the other two HPIs, which illustrate that terminal groups have strong influence on thermal performance. Moreover, different polydispersity and structure induce two distinct categories curves after 600 8C in Fig. 2, the reason behind is still unknown.
Fig. 1. 1H NMR spectrum of Ac-AMHPI.
1130
Z. Xu et al. / Chinese Chemical Letters 19 (2008) 1127–1130
Table 1 Syntheses and properties of prepared hyperbranched polyimides Entry
Ac-AMHPI PT-AMHPI AN-HPI AT-ANHPI
a
T d5 (8C)
455 530 467 533
b
T d10 (8C)
524 551 525 544
++: soluble at room temperatures; +: soluble at heating; the rate of 10 8C/min after annealing at 300 8C. a 5 wt% weight loss temperatures. b 10 wt% weight loss temperatures.
Mn
9,056 – – 12,194
Mw/Mn
2.48 – – 5.26
Solvents CHCl3
DMF/DMAC
THF
++ + + ++
++ ++ ++ ++
++ + + ++
Acetone
: insoluble at heating; the glass-transition temperatures was determinate under N2 and at
Fig. 2. TGA curves of HPIs.
All HPIs have good solubility in DMF, DMAc and NMP, even in THF and CHCl3, except that PT-AMHPI and ANHPI are soluble when heated in THF and CHCl3. Additionally, the serial of higher Mw/Mn have better solubility approved by comparing PT-AMHPI with AT-ANHPI in THF/CHCl3. In summary, HPIs with different terminal groups were synthesized by A2 + B3 method and performed good solubility and excellent thermal properties. Two factors, terminal groups and hyperbranched structure, impact important influence on the performance of the resultant HPIs and further research is in progress. Acknowledgments The program was financially supported from the National Natural Science Foundation (No. 50673031) of China and authors would like to extend thanks to Professor Yongming Chen at CAS. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]
Y.H. Kim, O.W. Webster, J. Am. Chem. Soc. 112 (1990) 4592. Y.M. Kim, R. Beckerbauer, Macromolecules 27 (1994) 1968. J.H. Fang, H. Kits, K. Okamoto, Macromolecules 33 (2000) 4639. P.D. Bartlett, M.J. Ryan, S.G. Cohen, J. Am. Chem. Soc. 64 (1942) 2649. D.T. Mcquade, T.M. Swager, Chem. Rev. 100 (2000) 2537. T.M. Long, T.M. Swager, J. Mater. Chem. 13 (2002) 3407. N.T. Tsui, A.J. Paraskos, L. Torun, et al. Macromolecules 39 (2006) 3350. B.S. Ghanem, K.J. Msayib, N.B. Mckeown, et al. Chem. Commun. (2007) 67. T.R. Kelly, X. Cai, F. Damkaci, et al. J. Am. Chem. Soc. 129 (2007) 376. Z. Chun, C.F. Chen., J. Org. Chem. 71 (2006) 6626.