End-Capping Reactions

The macroazoinimer obtained by the end capping reaction of polyazoester with a diizocyanate and hy-droxyethyl methacrylate was used in wood impregnation leading to the one-shot polymerization of styrene thermally [50]. 

The oxocarbenium perchlorate C(CH20CH2CH2C0+C104 )4 was employed as a tetrafunctional initiator for the synthesis of PTHF 4-arm stars [146]. The living ends were subsequently reacted either with sodium bromoacetate or bromoisobutyryl chloride. The end-capping reaction was not efficient in the first case (lower than 45%). Therefore, the second procedure was the method of choice for the synthesis of the bromoisobutyryl star-shaped macroinitiators. In the presence of CuCl/bpy the ATRP of styrene was initiated in bulk, leading to the formation of (PTHF-fc-PS)4 star-block copolymers. Further addition of MMA provided the (PTHF-fr-PS-fc-PMMA)4 star-block terpolymers. Relatively narrow molecular weight distributions were obtained with this synthetic procedure. 

Mono- and bifunctionally living poly(DMS) were produced by the method reported previously.7 The end-capping reaction of the living poly(DMS) was carried out by adding... 

It was found, however, in the course of the present study that the catalytic activity of the commercial Pt/C catalyst for the present hydrosilation reaction was not reproducible from one lot to another. Hence, we have developed an alternative process to produce la and l a, i.e. the direct end-capping reaction of mono- and bifunctionally... 

In order to synthesize polyfpropylene imine) dendrimers onto polystyrene via the divergent method, well-defined primary amine functionalized polystyrene had to be prepared as the core molecule. The anionic polymerization technique was chosen for the preparation of polystyrene (PS), because of the possibility of control over molecular weight and end group functionalization. An indirect amination procedure was developed [50], In this procedure a standard quantitative end-cap reaction with CO2 is used and a spacer is created between polystyrene and the primary amine function. The obtained polystyrene-COOH (PS-COOH), with Af around 3kgmol and values around 1.05, could be quantitatively reduced to the... 

One interesting aspect of this PS-MA synthesis is the possibility of modifying the amphipolarity of these macromonomers in the end capping reaction of the polystyryl anion with ethylene oxide (EO), as shown schematically in Scheme 16. Contrary to the literature report [181] that only one EO unit is added to the carbanion chain end in benzene solution under the reaction conditions used (40 °C), we have found that a higher conversion of... 

In 1992, Harada et al. prepared a compound in which many cyclodextrins are threaded on a single PEG chain and are trapped by end-capping groups at both termini of the main chain (Scheme 16) [111]. The pseudopolyrotax-ane formed in water from PEG bisamine (mass 3350) and a large excess of a-cyclo dextrin in an aqueous solution was isolated and then subjected to end-capping reaction with 2,4-dinitrofluorobenzene in DMF to yield polyro-... 

Another approach involves the end-capping reaction of living polystyrene with propylene oxide and the subsequent treatment of the alkoxide with bicyclo [2.2.1] hept-5-ene-2,3-rra s-dicarbonyl chloride to provide a macromonomer having a double bond in the middle of the polymer chain [88], as is shown in the following reaction (Scheme 33). 

Functional initiators have also been used for the synthesis of macromonomers by free radical processes. 2-2/-Azobis(N-N/-dimethylene isobutyramidine) was used to prepare imidazol terminated PS followed by an end-capping reaction with chloromethylstyrene [ 158]. A similar initiator was used for the radical polymerization of vinyl acetate (VAc) followed by reaction with chloromethylstyrene or methacryloyl chloride [159] (Scheme 47). 

The characterisation of novel a-PHB telechelics has been thus accomplished with the aid of ESI-MS" analysis, and the convenience of this technique for evaluation of polymer end-capping reactions has been demonstrated. 

K. Yamanaka, M. Jikei, M. Kakimoto, Preparation of hyperbranched aromatic polyimide without linear units by end-capping reaction. Macromolecules, 34, 3910-3915 (2001). 

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