142 Advances in Polymer Science Editorial Board: A. Abe. A.-C ...

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18 B. Charleux, R. Faust initiators for the living cationic polymerization of IBVE in conjunction with either ZnCl 2 , or EtAlCl 2 in the presence of a base such as 1,4-dioxane. The polymerizations of IBVE were carried out with the multifunctional initiators 8 and 9 in conjunction with EtAlCl 2 and 1,4-dioxane (10 vol.% to the solvent) in n-hexane or toluene at 0 °C. To determine their initiating efficiency, the polymerization rates observed with these multifunctional initiators were compared with those observed with their respective monofunctional counterparts at the same concentration of initiating functions. For each system, the polymerization rates were found to be in good agreement indicating that the concentration of growing species was identical, i.e., all functions have initiated. The MWs, determined by SEC with polystyrene calibration, were about three times higher with the trifunctional initiators compared to the monofunctional analog, and the polymers exhibited narrow MWD. For instance, initiator 8 at 3.5 mmol l –1 concentration was used to polymerize IBVE at a concentration of 0.76 mol l –1 . SEC analysis of the polymer gave apparent M n =23,300 g mol –1 (M w /M n =1.08) at complete conversion; using the monofunctional analog at 10 mmol l –1 concentration the polymer had M n =8100 g mol –1 (M w /M n =1.06). It was also found that additional feeds of monomer after complete conversion of the first monomer increment led to a linear increase of MW in direct proportion with conversion. After quenching with methanol or sodiomalonic ester, the number average end functionality (F n), calculated using 1 H NMR spectroscopy based on integration of characteristic peaks of terminal function and initiator residue, was found to be close to three. Hydrolysis of the ester core of the star polymer obtained with initiator 9 led to a poly(IBVE) with M n one third of the star itself and the MWD remained narrow. Moreover, 1 H NMR spectrum of the isolated arms indicated the expected structure with the hydroxyl terminal function. From this experimental evidence, the authors concluded that well-controlled three arm stars of poly(IBVE) were synthesized for the first time with this monomer. The star pol- (8) (9)
Synthesis of Branched Polymers by Cationic Polymerization 19 ymer from initiator 9 had exactly three arms with uniform and controlled length obtained by a living process and, after quenching, one terminal function per arm. The same conclusion was reached with initiator 8 although no direct experimental evidence of the structure could be given since the arms could not be separated from the core. To produce four arm star polymers of IBVE the use of a tetrafunctional initiator (10) with four trifluoroacetate goups linked to a cyclohexane core was also investigated by the same group [21, 22]. The monomer was polymerized under the same conditions as previously described and the same kinds of analysis were performed. Comparison of rates and MWs with those of the polymerization initiated with the monofunctional analog at a four times higher concentration led to the conclusion that four living arms were growing from the tetrafunctional core. When using a monomer concentration of 0.76 mol l –1 and an initiator concentration of 2.5 mmol l –1 , SEC measurements based on polystyrene calibration gave an apparent M n=28,000 g mol –1 (M w/M n=1.08) whereas 8100 g mol –1 (M w/M n=1.06) was obtained with the monofunctional initiator at 10 mmol l –1 . A value of F n close to 4 (3.77–3.91) was calculated using 1 H NMR spectroscopy after termination with the sodium salt of benzyl malonate. 2.2.1.2 Poly(p-methoxystyrene) n (10) Two derivatives of the trifunctional initiators 8 and 9 (respectively, 11=CH 3 -C[p- C 6 H 4 OCH 2 CH 2 OCH(CH 3 )-I] 3 and 12=C 6 H 3 -(1,3,5-)[COOCH 2 CH 2 OCH(CH 3 )-I] 3 ) with an iodine atom at the place of the trifluoroacetate group were used to synthesize three arm star polymers of p-MOS using living cationic polymerization with ZnI 2 as an activator in toluene at –15 °C [23]. With the typical conditions: [p-MOS] 0 =0.38 mol l –1 , [11] 0 =[ZnI 2 ] 0 =3.3 mmol l –1 , living polymerization of p- MOS was observed, i.e., a linear increase of MW with conversion and narrow MWD (M w /M n
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Page 3 and 4: Branched Polymers I Volume Editor:
Page 5 and 6: Volume Editor Dr. Jacques Roovers I
Page 7 and 8: Preface While books have been writt
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Page 11 and 12: Synthesis of Branched Polymers by C
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Synthesis of Branched Polymers by C
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72 N. Hadjichristidis, S. Pispas, M
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Poly(macromonomers): Homo- and Copo
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Author Index Volumes 101-142 Author
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Author IndexVolumes 101-142 231 Dun
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Author Index Volumes 101-142 233 Ka
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Author Index Volumes 101-142 235 Og
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Author Index Volumes 101-142 237 Su
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Subject Index Addition-fragmentatio
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Subject Index 241 Microphases 11z,
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