Macromolecules,Vol.38.No.5.2005 Communications to the Editor 1545 References and Notes as entry of the the M.Chem. ohtenolWaanictwltpartdeondnaegloneatod kDa8 his may be due to the increased surface area of eill,M. .P.M ,.ZJ 2838-28 C.D. ofPMVE-MA6 ie the pg。 )A An -PMVE-MA 199730,745 er con 14.2wt%L.e. 显是监A动 (10) one.J.M:Riddick.L Proc.NOBCChE 1999.26.53- (11)Baradie,B.:Shoichet,M.Mac .35,3569 (12) elas,D.A.;DeSimone.J.M.Macromolecules 1997,30. e ure 2).and 品无 (13) wwdle,S.M:Winder,R.J M. .c3 20036,47797 the (16) faeaepHceaimophol (17 (18) D.A.;Bet D.E De at 200-500 nm)has the first time by (20) J.:DeSimo M.Macromolecules 200,3,1565- (22) U.:Klo A P. the effect pe of 兰女 199 24 A:Do J (25) (26) M.K200 (27)Tai. Dr.D.Bratton,and Mr.C.J.Dux and ao是8 (28) Biss 美骨 (29) e8. M.R OConnor.s:Winder.R.J. (30)Liu.J:Tai,H:Howdle,S.M.Polyn 200546.1467-1472. F-PMVE-MA MA048270Fversion 5 wt %) indicate that a high monomer concen￾tration leads to a higher molecular weight product with very well-defined particles (C in Figure 2). To further investigate the effect of monomer conversion on the molecular weight and morphology of PVDF product, an experiment (entry 9) using the same conditions as entry 6 was carried out but terminated at a higher monomer conversion, obtaining a higher solid content in the autoclave (89 g/L). The morphology of the product obtained was a mixture of particles and agglomerated material. This indicated that, with monomer conversion increasing, the stabilization of F-g-PMVE-MA was not sufficient to prevent primary particles from aggregating. This may be due to the increased surface area of polymer as polymerizations progress, leading to a short￾age of F-g-PMVE-MA to stabilize the polymer. If this explanation is correct, then increasing stabilizer con￾centration should solve the problem. An experiment (entry 10) was carried out using 5 wt % F-g-PMVE-MA. Not surprisingly, a good morphology polymer was obtained at the monomer conversion of 14.2 wt %; i.e., the solid content in the autoclave is 89 g/L. Comparative experiments (entries 5 and 8 in Table 1) in the absence and presence of PDMS-ma stabilizer were carried out under the same reaction conditions as for experiment entry 6. In the absence of stabilizer, no primary particles were observed (A in Figure 2), and the PVDF polymer was only obtained as a spongy solid (A′ in Figure 2). When using PDMS-ma as the stabilizer, the primary particles were aggregated and formed large particles (diameter ca. 200-500 µm) (B and B′ in Figure 2). By contrast, using the graft stabilizer F-g-PMVE￾MA, the primary particles (diameter ca. 200-500 nm) were found to have a well-defined spherical morphology (C in Figure 2) and did not aggregate significantly (C′ in Figure 2). Conclusions. A high molecular weight product with well-defined and uniform spherical particles (diameter at 200-500 nm) has been obtained for the first time by dispersion polymerization of VDF in scCO2 using a fluorinated graft copolymer F-g-PMVE-MA as the sta￾bilizer. Further results detailing our investigation into the effect of stabilizer architecture for this type of graft stabilizer, including the addition of fluorinated graft chains with different chain lengths, varying the degree of graft chain incorporation, and the use of a longer polymer backbone, will be reported shortly. Acknowledgment. We gratefully acknowledge the European Community for funding (ECOPOL Project GRD1-2001-40294). We also thank Miss H. M. Woods, Dr. D. Bratton, and Mr. C. J. Duxbury for advice and help. S.M.H. is a Royal Society Wolfson Research Merit Award holder. 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