End-capping agent

Synthesis of the End-Capping Agent 4- (m-Hydroxyphenyl) -2-methyl-3-butyn-2-ol 1 ... 

The utility of a palladium catalyst in the synthesis of substituted aryl acetylenes is well established.(7,8,9,10) The end-capping agent I was produced by using a standard catalyst system, dichlorobls(triphenylphosphlne)palladlum (II)/copper (I) iodide/triphenylphosphlne mixture, which has been employed in previously developed ethynylation procedures.(10) The copper (I) iodide is believed to act as a cocatalyst, reducing the palladium (II) complex to the active palladium (0) catalyst. The scheme is shown in Figure 3 (diethylamine is the solvent).(11)... 

The Step 2 product was dissolved in THF and treated with one equivalent of 0.5 M sodium methoxide in methanol at ambient temperature. The mixture was then treated with between 25 and 50 equivalents of propylene sulfide and polymerized for 30 minutes. It was further treated with approximately 10 equivalents of poly (ethylene glycol) monoacrylate as the end-capping agent. The reaction mixture was stirred overnight at ambient temperature and isolated by precipitation in methanol. 

Entry Catalyst (mmol) Monomer (mmol) End-Capping Agent (mmol) Pyridine (mmol) Calculated M (daltons) Measured M (daltons) PDI... 

The addition polymerization has not a living character and leads to hydroxyl ended PEtG chains which have to be end-capped similarly to other polyaldehydes (4). As recommended by the literature, we used phenyl isocyanate (2) as an end-capping agent. 

Sample Identification. Given the number of samples and compositions, a general code was created as explained in Table II. In this table, the polyol type is identified by molecular weight and ethylene oxide content. Thus 40/15 refers to a polyol with M = 4000 and 15% (w/w) of ethylene oxide end capping agent. The last two labels in Table 2 indicate mold temperature and catalyst content. 

Another route to synthesizing star polymers by living polymerization involves the use of multifunctional end-capping agents, but this method is not suited for metal-catalyzed radical polymerizations, at least so far, due to the lack of universal and convenient terminating agents, as described above (section III.B.2). 

Concerning the synthesis of VAc macromonomer, Fukutomi et al. [270] showed a functionality of 1.78 per polymer chain. This result was attributed to side reactions of chloromethylstyrene (end-capping agent) onto - N = sites... 

No. Monomer Initiator End-capping agent Conditions Properties Ref. 

Phenylethynyl)-l, 2-benzenedicarboxyUc acid anhydride (PEPA) is used to introduce functional groups Pis, in order to make them heat curable. Citraconic anhydride (CA) acts in the same way. In addition, these modifiers act as end capping agents. 

The sodium salt of malonate carbanions reacts quantitatively with the living ends of poly(vinyl ether) s to give a stable carbon-carbon bond. This reaction was used to functionalize the ends of Hving poly(isobutyl vinyl ether) or poly(benzyl vinyl ether) with a vinyl ether polymerizable end group supported by a malonate ion (end-capping agent, 7) [151]. 

Recently a series of papers was published in which the end-group modification of the step-growth polymers polyamide 6 [71-73] and poly(butylene ter-ephthalate) [74] in SCCO2 was described. In some cases, the carbon dioxide, in which the end capping agent was dissolved, also contained a polar additive in order to enhance the sorption of the sc fluid by the relatively polar polymers. These papers illustrate the scope and limitations of the SCCO2 modification technique in a rather complete and subjective way, which wiU be discussed in detail in the rest of this chapter. 

Table 7. Table of end capping agents for anionically prepared polystyrene. ... 

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