Trifunctional vinyl ether

The key to this initiation is the trifunctional vinyl ether (16) from which the corresponding trifunctional initiator (17) is prepared by the addition of 3 equivalents of trifluoroacetic acid. Note that the three initiating sites in 17 are well separated spatially from each other by the rigid and planar triphenylmethyl core to avoid intramolecular side reactions be-... 

Figure 9 Plots of tan 5 as a function of temperature. In sample a, trifunctional thiol small molecules and trifunctional vinyl ether small molecules are mixed in the ratio 1 1, allowing for only thiol-ene reaction. In samples b-j, polymeric diacrylate is added to this mixture, increasing from 10% in sample b to 90% in sample j. Sample /r is the result of photopolymerization of the diacrylate in the absence of thiol. Radical transfer from acrylate chains to thiols results in shorter acrylate chains, and thus in flexibility and heterogeneous free volume distribution. Data obtained at a scan rate 2° C min" . ...

Three arm amphiphilic star block copolymers of IBVE and 2-hydroxyethyl vinyl ether (HOVE) were prepared using the trifunctional initiator 8 with sequential cationic polymerization of two hydrophobic monomers, IBVE and AcOVE. Subsequent hydrolysis of the acetates led to the hydrophilic poly(HOVE) segments [38]. Two types of stars were prepared depending on which monomer was polymerized first three arm star poly(IBVE-h-HOVE), with the hydrophobic part inside and three arm star poly(HOVE-h-IBVE), with the hydrophobic part outside. When IBVE was polymerized first, the experimental conditions were the same as described in Sect. 2.2.1. After reaching quantitative monomer conversion, AcOVE was added and temperature was raised from 0 to 40 °C to accelerate the reaction since this monomer is less reactive than IBVE. When starting with AcOVE as a first block, both polymerizations were carried out at 40 °C. SEC analysis showed that MWDs were narrow for the two steps whatever the se-... 

Scheme 9 Synthesis of triarmed poly(vinyl ethers) with a trifunctional initiator...

On the basis of these studies, a tetrafunctional silyl enol ether (18) carrying four such enolate functions has been prepared the corresponding trifunctional compound is also available [142]. These silyl enolates effectively couple living poly(vinyl ethers) with the chloride counteranion to form tri- and tetraarmed polymers (e.g., 19, Scheme 10) [205]. Similar chemistry also operates with living cationic poly(a-methylstyrene) but specifically needs the additional use of an amine to accelerate the release of the trimethylsilyl groups [159,207]. 

Three arm amphiphilic star-block copolymers of isobutyl vinyl ether (IBVE) and 2-hydroxyethyl vinyl ethers were also prepared by Higashimura et al. [23]. The synthetic strategy involved the sequential living cationic polymerization of IBVE and 2-acetoxyethyl vinyl ether, initiated by the trifunctional initiator system composed of tris(trifluoroacetate) and ethylaluminum dichloride, with excess of 1,4-dioxane as a carbocation-stabilizing Lewis base (Scheme 8). 

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