1、Ring-Opening Polymerization of 1-Caprolactone Initiated byCyclopentadienyl SodiumMINGLONG YUAN, CHENGDONG XIONG, XIANMO DENGChengdu Institute of Organic Chemistry, Academia Sinica, P.O. Box 415, Cheng-du 610041, Peoples Republic of ChinaReceived 31 July 1996; accepted 9 August 1997ABSTRACT: Polymeri
2、zation of 1-caprolactone had been investigated with cyclopentadi-enyl sodium as an initiator. The effects of reaction time, temperature, and concentrationof the initiator on the yield and molecular weight of the polymer were discussed. Itwas shown that the high molecular weight of poly(1-caprolacton
3、e) (13 1 104) wasobtained with cyclopentadienyl sodium initiator, and the mechanism of polymerizationwas also discussed. q 1998 John Wiley ring-opening polymerization; cyclopentadienyl sodiumINTRODUCTION ganoalkali initiators.1120But, during polymer-ization, the side reactionsuch as chain trans-fer2
4、1caused the reduction of the molecularPolymerization of lactones is one of the mostweight of PCL. So, it was difficult to obtain highextensively studied types of ring-opening poly-molecular weight of the polymer by present an-merization.1,2The ring-opening polymerizationionic polymerization mechanis
5、m. Based on theof 1-caprolactone (CL) has been of particularproblems previously described, it is proposed tointerest because of the biodegradability andsubstitute heavy metal tin with a nontoxic coun-permeability of poly(1-CL) (PCL) for the po-terpart (e.g., sodium) that should give a reason-tential
6、 use in drug delivery systems.3In gen-able molecular weight. This article describes theeral, polymerization of CL should be conductedanionic polymerization of CL initiated by cyclo-in the presence of some initiators to get fastpentadienyl sodium (CpNa) and the characteriza-reaction and high molecula
7、r weight. Tin salts,tion of resulting polymers.such as tin(II)octoate or SnCl4,310are themost widely used initiators for the polymeriza-tion of CL and other lactones. However, PCLfree of heavy metal ions is preferable when itEXPERIMENTALis used in medical and pharmaceutical appli-cations. Therefore,
8、 there is a need to replaceMaterialsthe tin-based initiators by using less poisonous1-CL from Aldrich Chemical Co. (Milwaukee,ones.WI) was dried over calcium hydride and dis-Anionic polymerization of CL was studied bytilled under vacuum before use. Cyclopentadi-using alkoxide, alkyl lithium, and oth
9、er or-ene was prepared from dicyclopentadiene (pur-chased from Aldrich Chemical Co.) by heatingCorrespondence to: M. Yuan.and distilling at 1807C.Contract grant sponsor: National Natural Science Founda-Toluene, benzene, and tetrahydrofuran (THF)tion of China.was dried by refluxing over metal sodium
10、and dis-Journal of Applied Polymer Science, Vol. 67, 12731276 (1998)q 1998 John Wiley after further reaction, the yield andmolecular weight of PCL dropped due to the pos-sible side reaction occurring. It was demon-strated by Gross and colleagues24and Krichel-dorf and Boettcher25that t-BuOk and n-but
11、yl-Li can initiate anionic polymerization of lactidein toluene. They found that the polymerizationof lactide reacted by the deprotonation of mono-mers eqs. (1) and (2)and by the direct nucleo-philic attack of monomer onto a carbonyl groupeq. (3). Similar to that, we suggested that po-lymerization of
12、 CL initiated with CpNa be asdescribed.Polymerization of CL with CpNa possiblycaused the following equilibriums eqs. (4)and (5):(CH ) Ccurrency1O 1 CpCH O(CH ) Ccurrency1O 1 O(CH ) COCH OOcurrency1CO(CH ) COO(CH ) CO(CH ) Ccurrency1O 1 CpHCHO(4)(CH ) O8e13 4780/ 8E13$4780 12-06-97 10:14:41 polaas W:
13、 Poly Applied1276 YUAN, XIONG, AND DENG3. A. Schindler, Biodegradable polymer far sustaineddrug delivery, in Contemporary Topics in PolymerScience, Vol. 2, Plenum Press, New York, 1977, p.251.4. E. E. Schmitt and R. A. Polistina, U.S. Pat.(CH ) Ccurrency1O 1 CpCH OOCH COOCH COCp (5)3,297,033 (1967)
14、and U.S. Pat. 3,463,158 (1969)(to American Cyanamid Co.); Chem. Abstr., 66,To study the true equilibrium of polymeriza-P38656u (1967) and Chem. Abstr., 71, P92382ttion, we characterized the structure of PCL with(1969).IR and1H-NMR. The IR spectrum of PCL showed5. Ethicon, Inc., Ger. Offen. 2,162,900
15、 (1972), Chem.that the absorption bands at 1756 cm01, 2946Abstr., 76, P73051w (1972).cm01, and 1173 cm01, are due to C|O, CH6. B. Ething, S. Gogolewski, and A. Pennings, J.of CH2and CO stretch, respectively. The Polym., 23, 1587 (1982).7. R. Vasantharamari and A. Pennings, J. Polym., 24,absorption b
16、and at 3510 cm01is assigned to175 (1983).terminal hydroxy groups. This is in accordance8. F. E. Kohn and J. G. Van Ommen, Feijin, J. Eur.with ref. 26. From the IR spectrum of PCL, noPolym., 19, 1081 (1983).cyclopentadienyl end groups were found. The1H-9. W. Dittrich and R. C. Schulz, Makromol. Chem.
17、,NMR spectrum of PCL (Fig. 1) shows the peaks15, 109 (1971).at (CH2)4, COCH2, and OCH210. J. Kleine and H. Kleine, Makromol. Chem., 30, 23methylene protons, respectively. The1H-NMR(1959).spectrum of PCL with CpNa is in accordance with11. E. W. Fischer, H. J. Schulz, and G. W. Kolloid, Poly-ref. 27.
18、Also, no cyclopentadienyl end groups weremer, 251, 980 (1973).12. E. F. Cox and F. Hostettler, U.S. Pat. 3,021,313found from the1H-NMR spectrum of PCL. It indi-(1976).cated that ring-opening polymerization of CL ini-13. E. F. Cox and F. Hostettler, Brit. Pat. 981,199tiated by CpNa was mainly through
19、 the deproto-(1965).nation of the monomer Eq. (4) and not quite14. E. F. Cox and F. Hostettler, U.S. Pat. 3,021,309through direct nucleophilic attack onto a carbonyl(1962).group of monomers. The single active center pro-15. R. Perret and A. Skoulios, Makromol. Chem., 152,duced during polymerization
20、is the effective start-291 (1972).ing point from which high molecular weight PCL16. A. Deffieux and S. Boileau, Macromolecules, 2, 369was obtained. However, in other anionic polymer-(1976).ization, both ways of chain propagations coexist.2517. K. Ito, Y. Hisazuka, and Y. Yamashita, Macromole-cules,
21、10, 821 (1977).In conclusion, CpNa is an effective initiator for18. K. Ito and Y. Yamashita, Macromolecules, 11, 68the polymerization of CL, and the initiator is non-(1978).toxic and convenient to prepare. High molecular19. Y. Yamashita, Polym. Prepr., 21, 51 (1980).weight PCL (10 1 104) can be obta
22、ined by using20. P. Sigwalt, Angew. Makromol. Chem., 94, 161CpNa as an initiator.(1981).21. H. R. Kricheldorf and I. Kreiser-Saunders, Makro-The authors acknowledge partial financial support frommol. Chem., 191, 1057 (1990).the National Natural Science Foundation of China.22. J. Hewscher, R. Jerome,
23、 and J. P. Bioul, Int. Rev.Sci., Phys. Chem., Ser. 2, 8, 192 (1975).23. W. X. Cao, G. F. Lin, and X. D. Feng, Polym. Bull.,20, 111 (1988).REFERENCES24. R. A. Gross, G. Zhang, G. Konrad, and R. W. Lenza,Macromolecules, 21, 2657 (1988).1. J. M. Vion, R. Jerome, P. Teyssie, M. Aubin, and25. H. R. Krich
24、eldorf and C. Boettcher, Makromol.R. E. Prudhomme, Macromolecules, 11, 1828 Chem., Macromol. Symp., 73, 47 (1993).(1986). 26. X. M. Deng, Z. X. Zhu, and C. D. Xiong, J. Appl.2. S. J. Ory, C. B. Hammond, S. G. Yancy, R. W. Hen- Polym. Sci., 64, 1295 (1997).dren, and C. G. Pitt, Am. J. Obstet. Gynecol., 145, 27. Ph. Dubois, R. Jerome, and Ph. Teyssie, Macromol-ecules, 24, 977 (1991).600 (1983).8e13 4780/ 8E13$4780 12-06-97 10:14:41 polaas W: Poly Applied
