Synthesis of Telechelic Oligomer Precursors

The chain-end halogen atom can be replaced by various methods, such as nucleophilic substitution or radical coupling. These techniques are developed next. 

The halogen end group can be transformed into other functionalities by means of standard organic procedures, such as a nucleophilic displacement reaction. Different authors have investigated this process of the nucleophilic displacement reactions with model compounds, to confirm the feasibility and selectivity. Compounds such as 1-phenylethyl halide, methyl 2-bromopropionate, and ethyl 2-bromoisobutane mimic the end groups of PSs, poly(alkyl acrylates), and poly(alkyl methacrylates), respectively. Different compounds have been tested, such as sodium azide, n-butylamine, and n-butylphosphine. 

The reactions of the model compounds with sodium azide were performed in DMF at room temperature, with 1.1 equiv of sodium azide [130-132]. The kinetics of these reactions was followed by gas chromatography and the rate constants were calculated. The kinetics show that the reaction of the bromi- 

It is also possible to use the trimethylsilyl azide in the presence of tetra-butylammonium fluoride to transform the terminal halide into an azide group. 

The halogen functional polymer can react with a thiol by nucleophilic reaction, resulting in a polymeric thioether and a hydrogen halide. The latter is trapped by a basic additive, preventing a reverse reaction. Snijder et al. [135] used this technique to modify the end group of poly( -butyl acrylate) into a hydroxy-functional polymer. With 2-mercaptoethanol, the yield of functionalization was higher with the addition of 1,4-diazabicyclo[2,2,2]octane (DABCO) to the reaction mixture. The addition of DABCO allows for the formation of a sulfide anion, which is a stronger nucleophile. They studied this 

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