Effect of variations of CuIIX2/L, surface area of Cu0, solvent, and temperature on atom transfer radical polyaddition of 4-vinylbenzyl 2-bromo-2-isobutyrate inimers

Abstract

An asymmetrical AB type inimer (4-vinylbenzyl 2-bromo-2-isobutyrate (VBBiB)) was synthesized and a variety of conditions for atom transfer radical polyaddition (ATRPA) of VBBiB was investigated regarding a CuX₂/Cu⁰/ligand catalytic system (where, X = Br or Cl; ligand = 4,4′-dinonyl-2,2′-bipyridine (dNBpy), N,N,N′,N′′,N′′-pentamethyl diethylenetriamine (PMDETA) or 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA)). We focused on investigation of the effect of four reaction factors, i.e. type of ligand, Cu⁰ surface area, solvent and temperature on the final structure and molecular characteristics of the polyesters. The VBBiB/CuBr₂/Cu⁰(wire)/PMDETA system showed formation of branched polymers due to very high activity of the catalyst complex. Replacing Cu⁰ wire with Cu⁰ powder, possessing higher surface area, resulted in only slight increase of the rate of inimer consumption. The polyaddition was more significantly affected by reaction temperature. Decreasing reaction temperature down to 0 °C increased significantly self-degradation by-products formation as a result of longer reaction times. Optimization of reaction conditions using commercially available catalytic systems allowed obtaining control over the polyester architecture and functionality, as well as ready achievement of functional linear polyesters with high molecular weight (M_w = 16 200).