Tunable amphiphilic graft copolymers bearing fatty chains and polyoxazoline: synthesis and self-assembly behavior in solution

Abstract

Amphiphilic graft copolymers composed of a methacrylate-based hydrophobic backbone with C₁₁ pending chains end-capped by hydrophilic polyoxazoline (POx) blocks were successfully synthesized using the grafting-onto method by associating reverse addition fragmentation chain transfer (RAFT) polymerization with azide–alkyne Huisgen's cycloaddition (CuAAC). Pure and well-characterized copolymers with different molecular weights and without traces of starting polymers were obtained. The hydrophilic character of the copolymers was controlled by copolymerizing the azido-terminated monomer 11-azido-undecanoyl methacrylate (AzUMA) with lauryl methacrylate (LM), the corresponding (co)polymers being then coupled with α-alkyne-POx. Using dynamic light scattering (DLS) and transmission electronic microscopy (TEM) techniques, their self-assembling behavior was studied by direct dissolution in water without further filtration. Depending on the systems, two or three particle size distributions co-exist in solution. However, the smallest objects, with D_H-values around 6, 42 and 255 nm, were obtained with the most hydrophilic copolymers (∼90% of hydrophilic group per molecule). Moreover, the influence of the starting copolymer architecture on its self-organization behavior was emphasized by comparing the self-assembly of the graft copolymers with that of an amphiphilic macromonomer, in situ polymerized, and whose structure mimics that of the repeating unit of the graft copolymers.