One-pot, three-step synthesis of amphiphilic comblike copolymers with hydrophilic backbone and hydrophobic side chains

A well-defined amphiphilic comblike copolymer consisting of a hydrophilic poly(-methacrylic acidi backbone and polystyrene [poly(St)] side chains was prepared by a one-pot, three-step successive method. First, the anionic copolymerization of two functional monomers, namely, 1-(ethoxy)ethyl methacrylate (EEMA) and a small amount of glycidyl methacrylate (GMA, was carried out in THF, using 1,1-diphenylhexyllithium (DPHL) as the initiator, in the presence of LiCl ([LiCl]/[DPHL](0) = 1), at -40 degrees C. The copolymer poly(EEMA-co-GMA) thus obtained possessed a controlled molecular weight and composition as well as a narrow molecular weight distribution (M-w/M-n = 1.09-1.13). Without termination and copolymer separation, an anionic living poly(St) solution was introduced into the above system at -40 degrees C. The coupling reaction (second step) between the epoxy groups of poly(EEMA-co-GMA) and the living sites of poly(St)s occurred rapidly, generating a comblike copolymer with a poly(EEMA-co-GMA) backbone and poly(St) side chains. This copolymer was Free of its precursors, and its molecular weight distribution was narrow (M-w/M-n = 1.14-1.21). In addition, the lengths of both the backbone and side chains, hence the total molecular weight of the copolymer, could be controlled. In the final step, the excess of unreacted epoxy groups in the backbone was reacted with DPHL or sodium ethoxide, and this was followed by the hydrolysis of EEMA units under acidic conditions. This procedure changed the EEMA units to methacrylic acid units by eliminating the protecting 1-(ethoxy)ethyl groups, and an amphiphilic comblike copolymer was thus obtained.