Jing Li( 李静， ), Xufeng Ni( 倪旭峰 ) Introduction Polymerization Features Mechanism of Polymerization Characterization and properties of PDEVP Reference 1 J. Ellis, A. D. Wilson, Dent. Mater. 1992, 8, 79–84. 2 H. Steininger, M. Schuster, K. D. Kreuer, B. Bingoel, W. H. Meyer, Phys. Chem. Chem. Phys. 2007, 9, 1764– T. Wagner, A. Manhart, N. Deniz, M. Wagner, W. H. Meyer, Macromol. Chem. Phys. 2009, 210, 1903– B. Bingol, W. H. Meyer, M. Wagner, G. Wegner, Macromol. Rapid Commun. 2006, 27, 1719– G. W. Rabe, H. Komber, L. Haeussler, K. Kreger, G. Lattermann, Macromolecules. 2010, 43, 1178– U. B. Seemann, J. E. Dengler, B. Rieger, Angew. Chem. Int. Ed. Engl. 2010, 49, 3489– S. Salzinger, U. B. Seemann, A. Plikhta, B. Rieger, Macromolecules. 2011, 44, 5920– N. Zhang, S. Salzinger, F. Deubel, R. Jordan, B. Rieger, J. Am. Chem. Soc. 2012, 134, 7333– Jing Li, Xufeng Ni*, Jun Ling, Zhiquan Shen, Journal of Polymer Science, Part A: Polymer Chemistry 2013, DOI: /pola Polymeric materials containing covalently bonded heteroatoms, particularly phosphorus containing polymers are interesting for a wide field of science and applications 1,2. To date, many attempts to polymerize vinylphosphonate monomers have been reported including radical polymerization 3, anionic polymerization 4 and rare earth catalytic polymerization 5-8. Here, we report the controlled polymerization of DEVP initiatedby lanthanide borohydrides, Ln(BH 4 ) 3 (THF) 3 (Ln = Y, La, Nd, Sm, Gd, Dy, Lu). The polymerization features, kinetics and mechanism of the polymerization are discussed; the structures and the properties of obtained poly(diethyl vinylphophonate)s (PDEVPs) are characterized 9. Conclusions Syntheses and Properties of Poly(diethyl vinylphosphonate) Initiated by Lanthanide Tris(borohydride) Complexes: Polymerization controllability and Mechanism Department of Polymer Science and Engineering, MOE Key Laboratory of Macromolecular Synthesis and Functionalization,Zhejiang University, Hangzhou, , China Acknowledgments The authors gratefully acknowledge the financial supports of the National Natural Science Foundation of China ( ) and the Special Funds for Major Basic Research Projects (G2011CB606001). Figure 1 Determination of the catalytic activity of Gd (BH 4 ) 3 (THF) 3, La(BH 4 ) 3 (THF) 3, Sm(BH 4 ) 3 (THF) 3 for the polymerization of DEVP Reaction conditions: 40°C, 1 h, in bulk, [M]/[Ln]=300. Figure 2 ln(M 0 /M) versus time for the polymerization of DEVP Conditions: [M]/[Gd]=300:1, 40°C, in bulk. Figure 8 1 H NMR spectra by Bruker Avance III 500 of oligomeric PDEVP terminated by ethyl iodide (Gd(BH 4 ) 3 (THF) 3, 10 eq DEVP) Figure 7 1 H NMR recorded by Bruker Avance III 500 of oligomeric PDEVP terminated by benzyl chloride (Gd(BH 4 ) 3 (THF) 3, 10 eq DEVP) Figure 6 ESI-MS analysis of oligomeric PDEVP (Gd(BH 4 ) 3 (THF) 3, 5 eq DEVP) Figure 3 Relationship of conversion and Mn, MWD in polymerization of DEVP Conditions: [M]/[Gd]=300:1, 40°C, in bulk Scheme 1 Polymerization mechanism of DEVP catalyzed by Ln(BH 4 ) 3 (THF) 3 Figure 5 Change of transmittance at λ=550 nm for PDEVP at 1 mg/mL catalyzed by Gd(BH 4 ) 3 (THF) 3 Figure 4 GPC trace of PDEVP catalyzed by Gd(BH 4 ) 3 (THF) 3 Reaction conditions: 40°C, 1 h, in bulk, [M]/[Ln]= Lathanide tris(borohydride) complexes, Ln(BH 4 ) 3 (THF) 3 (Ln = Y, La, Nd, Sm, Gd, Dy, Lu), have been applied to initiate the polymerization of DEVP. 2.The initiators exhibit high activities producing PDEVP in quantitative yields within 1 h polymerization. The kinetics of the polymerization indicates that the polymerization undergoes a controlled manner. 3.The thermal analysis of obtained PDEVPs shows a two-step decomposition and a Tg at about 262 o C. The thermosensitive behavior is observed by UV transmittance of aqueous solution of PDEVPs, which shows a LCST about 50 o C. 4.A coordination anion polymerization mechanism is proved by end group analysis using ESI-MS and NMR spectra. In order to figure out the polymerization mechanism, oligomers have been produced by using 5 to 1 ratio of DEVP to catalyst and are subsequently analyzed by ESI-MS. Besides, benzyl chloride and ethyl iodide are chosen to terminate polymerization of DEVP using 10 to 1 ratio of DEVP to catalyst. For all peaks in Figure 6, the molecular mass of the corresponding oligomers is found to be Mn(DEVP). n+2 g mol -1. The remaining 2 g mol -1 corresponds to two hydrogen atoms, one of which initiates chain growth and another of which comes from the termination reaction during moisture work-up. More evidences can be seen from analysis of end groups of oligomeric PDEVP terminated by benzyl chloride and ethyl iodide illustrated in Figures 7 and 8. From all results above, a coordination anion polymerization mechanism for the polymerization of DEVP catalyzed by Ln(BH 4 ) 3 (THF) 3 is shown in scheme 1. The catalytic activity of Gd(BH 4 ) 3 (THF) 3, La(BH 4 ) 3 (THF) 3 and Sm(BH 4 ) 3 (THF) 3 are measured as illustrated in Figure 1, and the results clearly reveal that the catalytic efficiency is strongly affected by the radius (and therefore also the Lewis acidity) of the lanthanide metal center. The kinetics of the polymerization is investigated, and a linear growth of ln(M 0 /M) with time can be observed which proves that the conversion increases with molecular weight and the catalyst has a highly catalytic activity from the start of polymerization (Figure 2). A linear relationship between the molecular weight and conversion proves that the polymerization can be controlled to a certain extent, but the plot without going through the origin indicates that it’s not a ‘real living polymerization’. All the polymers obtained have a similar unimodal distribution as shown in Figure 4. The amphiphilicity of PDEVP is further underlined by the existence of a lower critical solution temperature (LCST) of aqueous PDEVP solutions. PDEVP has a thermosensitive behavior which is transparent in water below 50 o C but turns to nontransparent over 50 o C ( Figure 5).