Free Radical-Induced and Pd(II) Complexes-Catalyzed Poly(norbornene) Formation

Transcription

1 Journal of the Chinese Chemical Society, 2003, 50, Free Radical-Induced and Pd(II) Complexes-Catalyzed Poly(norbornene) Formation An-chi Yeh ( ) Department of Chemical Engineering, Chengshiu Institute of Technology, Kaohsiung 833, Taiwan, R..C. The reactions of norbornene polymerization were catalyzed by Pd(CH 3 ) 4 (BF 4 ) 2 (1), AIBN (2), and [{(2,6-C 6 H 3 ( i Pr) 2 )N=C()} 2 Pd()(CH 3 )][BF 4 ](3) without using methylalumoxane (MA). These poly(norbornene)s are readily soluble in organic solvents such as toluene, dichloromethane and tetrahydrofuran. According to the NMR data, the end group of PNA resulting from the AIBN process is found from THF. The PNT resulting from the catalyst (1) shows bi-models of GPC bands (M n = 4236 and 66317), two glass transition temperatures (T g = 72.7 and C), as well as two decomposition temperatures (Td = 337 and 460 C). Keywords: Poly(norbornene); Norbornene; thylalumoxane (MA). INTRDUCTIN Scheme I Polymerization of norbornene with physical properties has been reported. 1 These products have high glass transition temperatures (Tg) and high decomposition temperatures (Td). Most poly(norbornene)s are insoluble in organic solvents. Several polymerization have been reported for the norbornene and norborneneethylene polymers with transition metal/methylaluminoxane (MA) cocatalysts This paper reports that norbornene polymerization can be catalyzed by Pd(II) complexes and N,N -azobis(isobutyronitrile) (AIBN) without the use of methylaluminoxane (MA) cocatalysts. These poly(norbornene)s are readily soluble in organic solvents such as toluene, dichloromethane and tetrahydrofuran (THF). RESULTS AND DISCUSSIN The reaction of norbornene polymerization can be catalyzed by Pd(II) complexes (catalyst Pd(CH 3 ) 4 (BF 4 ) 2 (1) and [{(2,6-C 6 H 3 ( i Pr) 2 )N=C()} 2 Pd()(CH 3 )][BF 4 ] (3)) and free radical (catalyst AIBN (2)) without methylalumoxane (shown in Scheme I). 1 H NMR and 13 C NMR analyses The 1 H NMR spectra of the poly(norbornene)s (PNT is poly(norbornene) with catalyst 1, PNA with catalyst 2 and catalyst 1. Pd() 4 (BF 4 ) 2 2. AIBN 3. N N Pd PND with catalyst 3) that have poly(norbornene) s characteristic peaks at the chemical shift of , as shown in Fig. 1, and 13 C NMR spectra have poly(norbornene) s characteristic peaks at the chemical shift of and , as shown in Fig. 2. Whereas the 13 C NMR spectrum of PNA shows the large resonance around which is totally absent in the Arndt hydrotrimer. 13 This resonance is barely present in the spectrum of the derived polymer. According to Arndt s report poly(norbornene)s contain mixed 2,3- and 2,7-enchainment. 13 That 13 C NMR data are identified for 2,3-enchainment and 2,7-enchainment for poly(norbornene) as shown in Fig. 3. PNA results with AIBN as a free radical initiator. The reaction products thus contain mixed 2,3- and 2,7-enchainment. ther poly(norbornene) products only contain NC BF 4 n

2 960 J. Chin. Chem. Soc., Vol. 50, No. 5, 2003 Yeh 2,3-enchainment moiety Scheme II The 1 H NMR chemical shifts of PNA show a peak at 3.80 and 3.68 with 1:2 integral ratios. They are assigned to the -CH and the -CH 2 -CH 2, which are of the end group of PNA as shown in Fig. 1. The 13 C NMR chemical shift at 83.2 and 67.5 are assigned to the -CH and -CH 2 -CH 2 group, respectively, as shown in Fig. 4. This result indicates that THF is incorporated into PNA as the end group. It is believed that the AIBN initiator is to first decompose to generate nitrogen and the resonance-stabilized cyanopropyl radical. The radical can transfer to the THF molecule that gives rise to cyanopropane and the THF radical. Addition of the THF radical to norbornene and the polymerization proceeds as shown in Scheme II. C N N C C + + N N + C HC + n Fig H NMR spectrum of polynorbornene involves PNT, PNA and PND. Molecular weight analysis and thermal properties The GPC analysis shows that the molecular weights of poly(norbornene)s fall in the region of 4200~66300 with PDI = 1.52~2.69. The PNT exhibits the bi-model distribution of molecular weights around with PDI = 1.71, and 4236 with PDI = 1.52; the other poly(noebornene)s molecular weights are around with PDI = 2.69 from PNA and 7231 with PDI = 1.59 from PND. The PNTs show two glass transition temperatures at 72.7 and C, and two decomposition temperatures at 337 and 460 C. PNTs have bi-model distribution of molecular weights that have a high molecular weight (66317) with a high glass transition temperature (201.5 C) and high decom ppm ,7-enchainment ppm ppm ppm ppm 2,3-enchainment Fig C NMR spectrum of polynorbornene involves PNT, PNA and PND. Fig C NMR spectra of 2,7-enchainment and 2,3- enchainment for poly(norbornene).

3 Catalyzed Poly(norbornene) Formation J. Chin. Chem. Soc., Vol. 50, No. 5, Fig. 4. 2D-HMQC NMR spectrum of PNA. Fig. 5. TGA curves for polynorbornene involves PNT, PNA and PND.

4 962 J. Chin. Chem. Soc., Vol. 50, No. 5, 2003 Yeh Fig. 6. DSC curves for polynorbornene involves PNT, PNA and PND. position temperature (460 C) and lower molecular weight (4236) with lower glass transition temperature (72.7 C) and lower decomposition temperature (337 C). The other poly- (norbornene)s glass transition temperatures are C with PNA and C with PND and decomposition temperatures are 275 C with PNA and 398 C with PND. Fig. 5 shows the decomposition temperature by thermogravimetric analysis (TGA) and Fig. 6 shows the glass transition temperature from differential scanning calorimetry (DSC). Random poly(norbornene) is obtainable with AIBN catalyst that polymer has lowest decomposition temperature (275 C). The poly(norbornene)s with relatively high crystallinity are obtained from the reactions using Pd(II) catalysts. They also show higher decomposition temperature in the region of 337~460 C. CNCLUSINS This paper reports that poly(norbornene) uses Pd(II) complexes and N,N -azobis(isobutyronitrile) (AIBN) without methylaluminoxane (MA). These poly(norbornene)s are soluble in organic solvents such as toluene, dichloromethane and tetrahydrofuran. The THF end group is identified from NMR spectra for PNA. PNT have bi-modal molecular weight, two glass transition temperatures and two decomposition temperatures. EXPERIMENTAL SECTIN General Procedures and Materials All work involving air- and/or moisture-sensitive compounds was carried out by using standard high-vacuum, Schlenk or drybox (M. Braun) techniques. An NMR spectrum was recorded on a Bruker 500 MHz instrument. A DSC analysis was recorded on a Perkin Elmer DSC-7 instrument. A TGA analysis was recorded on a Perkin Elmer Pyris 1 instrument. Gel permeation chromatographic (GPC) analyses utilized a Polymer Standards Service column (10 m gel. SDV linear, 60 cm), a Knauer HPLC Pump 64, and a Waters differential refractometer (R 401). All GPC analyses were

5 Catalyzed Poly(norbornene) Formation J. Chin. Chem. Soc., Vol. 50, No. 5, performed on solutions in toluene ( g/dl). Calibration was based on six polystyrene standards ranging from Mn 1300 to (Mw/Mn < 1.1). Dichloromethane was dried over CaH 2 and distilled. THF and Diethyl ether were dried over sodium benzophenone ketyl and distilled. Acetonitrile and D-chloroform were dried over CaH 2 and then vacuumtransferred. Nitromethane was dried by stirring over P 2 5 and then vacuum-distilled. [Pd(CH 3 ) 4 ][BF 4 ] 2 were prepared according to a procedure published by Schramm and Wayland. [{(2,6-C 6 H 3 (i-pr) 2 )-N=C()C()=N-(2,6-C 6 H 3 (i-pr) 2 )}- PdCl(CH 3 )][BF 4 ] was prepared according to a procedure published by Brookhart. 17 Polynorbornene with AIBN A 50 ml Schlenk flask was charged with 2 g (21.3 mmol) of norbornene and 70 mg (0.43 mmol) of N,N - azobis(isobutyronitrile) (AIBN) then vacuum-transferred 10 ml THF. After 16 h at 70 C, the polymer was isolated by precipitation with methanol. The product was dried at 80 C for 12 h. Yield: 1.43 g (71.5%); Mn(GPC) = 28878, Mw (GPC) = 77587, PDI(GPC) = H NMR (CDCl 3 ) (ppm): 3.80 (1H, br), 3.68 (2H, br), (m, br), 13 C NMR (CDCl 3 ) (ppm): 83.2, 67.5, 67.2, , , , , , Polynorbornene with [Pd(CH 3 ) 4 ][BF 4 ] 2 A 50 ml Schlenk flask was charged with 2 g (21.3 mmol) of norbornene and 95 mg (0.213 mmol) of [Pd- (CH 3 ) 4 ][BF 4 ] 2 then vacuum-transferred 10 ml nitromethane. After 20 h at 25 C, the polymer was isolated by precipitation with methanol. The product was dried at 80 C for 12 h. Yield: 1.68 g (84%); Mn (GPC) = 4236, Mw (GPC) = 7280, PDI (GPC) = 1.72, H NMR (CDCl 3 ) (ppm): (m, br). 13 C NMR (CDCl 3 ) (ppm): , , , , , Polynorbornene with [{(2,6-C 6 H 3 (i-pr) 2 )-N=C()C()= N-(2,6-C 6 H 3 (i-pr) 2 )}PdCl(CH 3 )][BF 4 ] A 50 ml Schlenk flask was charged with 2 g (21.3 mmol) of norbornene and 140 mg (0.213 mmol) of [{(2,6- C 6 H 3 (i-pr) 2 )-N=C()C()=N-(2,6-C 6 H 3 (i-pr) 2 )}PdCl- (CH 3 )][BF 4 ] then vacuum-transferred 10 ml dichloromethane. After 20 h at 25 C, the polymer was isolated by precipitation with methanol. The product was dried at 80 C for 12 h. Yield: 1.5 g (75%); Mn (GPC) = Mw (GPC) = PDI (GPC)= H NMR (CDCl 3 ) (ppm): (m, br). 13 C NMR (CDCl 3 ) (ppm): , , , , , ACKNWLEDGMENT We are grateful to the National Science Council, Taipei, Taiwan, R..C., for their financial support. Received November 21, REFERENCES 1. (a) Goodall, B. L.; Kroenke, W.; Minchak, R. J.; Rhoodes, L. F. J. Appl. Polym. Sci. 1992, 47, 607. (b) Goodall, B. L.; Kroenke, W.; Minchak, R. J.; Rhoodes, L. F. Proceedings of the Third International Business Forum on Specialty Polyolefins (SP 93), Schotland Business Research, 1993, p 381. (c) EP 1991, 445, 755 to Idemitsu Kosan. 2. (a) thler, C.; Risse, W. Makromol. Chem., Rapid Commun. 1991, 12, 255. (b) Seehof, N.; thler, C.; Breunig, S.; thler, C. J. Mol. Catal. 1992, 76, (a) Sen, A.; Lai, T. W. rganometallics 1982, 1, 415. (b) Sen, A.; Lai, T. W.; Thomas, R. J. rganomet. Chem. 1988, 358, Kaminsky, W. Stud. Surf. Sci. Catal. 1990, 56, (a) Kaminsky, A.; Noll, A. Polym. Bull. 1993, 31, 75. (b) Kaminsky, W. J. Chem. Soc. Walton Trans. 1998, Chu, P. P.; Huang, W. J.; Chang, F. C.; Fan, S. Y. Polymer. 2000, 41, Provasoli, A.; Ferro, D. R.; Tritto, I.; Boggioni, L. Macromolecules. 1999, 32, Tritto, I.; Marestin, C.; Boggioni, L; Ferro, D. R. Macromolecules. 2000, 33, Mohring, P. C.; Covile, N. J. J. rganomet. Chem. 1994, 479, Altamura, P.; Grassi, A. Macromolecules. 2001, 34, Cherdron, H.; Brekner, M.-J.; san, F. Angew. Macromol. Chem. 1994, 223, Harringhton, B. A.; Crowther, D. J. J. Mol. Catal. 1998, 128, Kaminsky, W.; Brak, A.; Arndt, M. Markromol. Chem. Macromol. Symp. 1991, 47, (a) Ruchatz, D.; Fink, G. Macromolecules. 1998, 31, (b) Ruchatz, D.; Fink, G. Macromolecules. 1998, 31, (c) Ruchatz, D.; Fink, G. Macromolecules. 1998, 31, 4681.

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