Tailor-made poly(ethyl acrylate) by atom transfer radical polymerization

Atom transfer radical polymerization (ATRP) of ethyl acrylate (EA) was carried out using different initiators, CuBr or CuCl as catalyst in combination with different ligands e.g., 2,2'-bipyridine (bpy) and N,N,N',N '' N ''-pentamethyl diethylenetriamine (PMDETA). Use of PMDETA as ligand resulted in faster polymerization rate (95% conversion in 15 min) than those using bipyridine (similar to 58% conversion in 10.5 h). This is due to the lower reduction potential of copper-amine than that of copper-bpy complex, resulting in higher rates of activation of dormant halides. Use of ethylene carbonate as solvent lead to faster polymerization rate and better control in polymerization when compared with p-xylene as solvent. The reaction temperature had a positive effect on polymerization rate and the optimum reaction temperature was found to be 90 degrees C. An apparent enthalpy of activation of similar to 85 kJ/mol was determined for the ATRP of ethyl acrylate, corresponding to an enthalpy of equilibrium of similar to 64 kJ/mol. By judicious choice of the reaction parameters it was possible to tailor the end group of the final polymer. MALDI-TOF-MS analysis and the chain extension experiment of poly(ethyl acrylate) (PEA) prepared using bpy as ligand showed the presence of -Br as the end group. On the contrary, when PMDETA was used as the ligand, the mass spectra analysis showed hydrogen terminated polymer as the major species towards the end of polymerization. (c) 2007 Wiley Periodicals, Inc.