Rational Selection of Initiating/Catalytic Systems for the Copper-Mediated Atom Transfer Radical Polymerization of Basic Monomers in Protic Media: ATRP of 4-Vinylpyridine

Abstract

The successful ATRP of a coordinating monomer, 4-vinylpyridine (4VP), in aqueous media at 30 °C is reported. In the presence of basic and nucleophilic monomers such as 4VP, the use of the chloride-containing ATRP initiating/catalytic system is essential to achieve good polymerization control and narrow molecular weight distribution. This is due to the significantly slower reaction of the monomer or polymer with secondary alkyl chloride-type dormant chain ends compared to their alkyl bromide counterparts. When a bromide-based ATRP initiating/catalytic system was used, the obtained polymers had polymodal molecular weight distributions reflecting the formation of branched chains, whereas the polymers obtained with chloride-based initiating/catalytic system had narrow, monomodal, and symmetrical molecular weight distributions. The polymerization of 4VP mediated by the CuI complex of 2,2‘-bipyridine was slow due to the low value of the ATRP equilibrium constant, in agreement with the low reducing power of the ...