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

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56 B. Charleux, R. Faust macromonomer [95, 96] was obtained with the following monomers sequence: n-butyl vinyl ether (BVE), VOEM, BzOVE, and 2-(vinyloxy)ethyl methacrylate, this latter monomer being used to incorporate a terminal methacrylate. The macromonomer was purified from by-products by preparative size exclusion chromatography. The second example was a heterodimer quenched with the malonate anion 36 [97]. It was prepared by a three step technique: quantitative addition of HI to the first vinyl ether, addition of one equivalent of a second monomer (preferably less reactive than the first one) in the presence of ZnI 2 , and finally quenching with 36 which allowed introduction of the polymerizable vinyl ether end group. Two macromonomers were synthesized by this method with the respective following sequence: BVE/BzOVE and 2-ethylhexyl vinyl ether/CEVE. 3.3.1.2.2 Poly(p-alkoxystyrenes) Owing to the lower stability of growing p-alkoxystyrene cations and to the possibility of several side-reactions, some end-capping agents which were successfully used for poly(vinyl ether)s such as sodiomalonic ester and tert-butyl alcohol, did not give end-functionalization with poly(p-alkoxystyrene) cations. In contrast, primary and secondary alcohols underwent quantitative reactions to give stable alkoxy functional groups. Thus, 2-hydroxyethyl methacrylate and acrylate were used to introduce a polymerizable group at the w end [98, 99]. Living cationic polymerizations of p-MOS and tBOS were carried out at –15 °C in toluene using HI/ZnI 2 as an initiating system. When the monomer conversion was complete, a large excess of the quencher was added, resulting in a quantitative functionalization. The polymerization was shown to be living and well-defined macromonomers with narrow MWD and one polymerizable acrylate or methacrylate functional group per chain were obtained. Heterotelechelic poly(p-MOS)s were also prepared by the combination of the functional initiator method and the functional end-capping method. This allowed the synthesis of a poly(p-MOS) macromonomer with one malonate diester at the a end and one methacrylate group at the w end. 3.3.1.2.3 Poly(styrene) The living cationic polymerization of styrene could be achieved using 1-phenylethyl chloride as an initiator in the presence of SnCl 4 and n-Bu 4 NCl. However, in contrast to vinyl ethers and p-alkoxystyrenes, quenching with usual bases such as methanol, sodium methoxide, benzylamine, or diethyl sodiomalonate led to the terminal chloride instead of the specific end group. This was explained by the very low concentration of cationic species in comparison with the dormant C-Cl end group and also by the low reactivity of this C-Cl functional group in substitution reactions. This was overcome using organosilicon compounds
Synthesis of Branched Polymers by Cationic Polymerization 57 such as trimethylsilyl methacrylate (42) and quantitative functionalization was achieved when the quenching reaction was performed at 0 °C, for 24 h, in the presence of a large excess of the quencher and low concentration of the Lewis acid [100]. The same functionalization reaction could also be performed successfully in two steps, starting from an isolated polystyrene with a 26 C-Cl terminal group. 3.3.1.2.4 Poly(isobutylene) (42) Allyl terminated linear and three arm star PIBs and epoxy and hydroxy telechelics therefrom have been reported by Ivan and Kennedy [34]. Allyl functional PIBs were obtained in a simple one pot procedure involving living IB polymerization using TiCl 4 as coinitiator followed by end-quenching with allyltrimethylsilane (43, ATMS). The procedure was based on an earlier report by Wilczek and Kennedy [101] that demonstrated quantitative allylation of PIB-Cl by ATMS in the presence of Et 2 AlCl or TiCl 4 . Structural characterization by 1 H NMR spectroscopy and end group titration by m-chloroperbenzoic acid demonstrated quantitative end allylation. Quantitative hydroboration followed by oxidation in alkaline THF at room temperature resulted in -OH functional PIBs, which were used to form PIB-based polyurethanes. Quantitative epoxidation of the double bonds was also achieved with m-chloroperbenzoic acid in CHCl 3 at room temperature, giving rise to macromonomers able to polymerize by ring-opening polymerization. A three arm star epoxy-telechelic PIB (M n =4500 g mol –1 ) with triethyl amine gave a strong rubber exhibiting ca. 300% elongation. 3.3.1.3 Chain End Modification of Poly(isobutylene) (43) The polymerizable function is incorporated by chemical modification of the a or w end group after isolation of the polymer. Although it is versatile since a wide variety of polymerizable groups can be incorporated, the method generally involves several steps. The synthesis of polyisobutylene methacrylate (MA-PIB) was first reported by Kennedy and Hiza [102]. The synthesis was accomplished by a multistep process. First IB was polymerized by the cumyl chloride/BCl 3 initiating system.
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142 Advances in Polymer Science Edi
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Branched Polymers I Volume Editor:
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Volume Editor Dr. Jacques Roovers I
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Preface While books have been writt
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Contents Synthesis of Branched Poly
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Synthesis of Branched Polymers by C
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Synthesis of Branched Polymers by C
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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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Subject Index Addition-fragmentatio
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Subject Index 241 Microphases 11z,
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