Difunctional And Polyfunctional Initiators Styrene Acrylate Atom Transfer Radical Polymerization Studies

A new type of difunctional initiator (benzyl dibromide, ethyl dibromoacetate) was proposed in this paper and used to synthesize poly (alkyl acrylate) based triblock copolymers such as PSt-PBA-PSt, PMMA-PBA-PMMA.The atom transfer radical polymerization (ATRP) of styrene in bulk and in aqueous solution with dimethylformamide (DMF) was investigated using CuBr/bpy catalytic system with 1-phenylethyl bromide and benzyl a,oc-dibromide as initiator respectively. The polymerization was well controlled. It suggests that 1-phenylethyl bromide and benzyl dibromide are good initiator for ATRP of styrene. Because of different concentration of each component in above systems, it doesn't show that benzyl a,a-dibromide is a difunctional initiator. When ATRP of styrene was investigated with 1-phenylethyl bromide/benzyl a,a-dibromide mixture as initiator, the GPC chromatogram shows two elution peaks and the molecular weighs of the peaks are approximately in a 2/1 ratio. It suggests that benzyl dibromide is a difunctional initiator of ATRP of styrene. The analysis of end group using 1H-NMR also proves the result above. Similarly, by way of GPC chromatogram we proved that ethyl dibromoacetate is a good difunctional initiator of ATRP of acrylate.In this paper, narrow molecular weight distribution poly (butyl acrylate) difunctional precursors were prepared by ATRP using ethyl dibromoacetate as initiator and CuBr/bpy complex as catalyst, in the present of ethylene carbonate (EC). Then, well-defined PSt-PBA-PSt triblock copolymers were prepared using bromine end capped poly (butyl acrylate) as difunctional initiator, CuCl/bpy or CuBr/bpy as catalyst. But only with CuCl/bpy as catalyst can well-defined PMMA-PBA-PMMA triblock copolymers be prepared using bromine end capped poly (butyl acrylate) as difunctional initiator. In addition, tetrafunctinal and hexafunctional initiators were prepared simply by esterification of chloride dichloroacetyl and confirmed by GPC and 1H-NMR.This work is useful for the preparation of four-armed and six-armed star polymers and TPEs with higher oxidation resistance and oil resistance.