Synthesis of adaptative and amphiphilic polymer model conetworks by versatile combination of ATRP, ROP, and "click chemistry"

Well-defined adaptative and amphiphilic polymer conetworks based on hydrophilic poly(N,N-dimethylamino-2-ethyl methacrylate) (PDMAEMA) and hydrophobic poly(ε-caprolactone) (PCL) have been prepared by combination of ATRP, ROP, and "Click chemistry." Telechelic α,ω-alkyne terminated PCL crosslinker was obtained by ring-opening polymerization (ROP) of CL in THF at 80°C initiated by 1,4-butanediol and catalyzed by tin(II) bis 2-ethyl hexanoate (Sn(Oct)₂), followed by the quantitative esterification of hydroxyl end-groups by activated 4-pentynoic acid. In parallel, an azido-containing PDMAEMA-based copolymer was obtained in a three-step strategy involving primarily the copolymerization of DMAEMA with newly synthesized 2-(2-azidoethoxy)ethyl methacrylate (AEEMA) monomer. The latter was obtained by nucleophilic substitution of chloride atom from 2-(2-chloroethoxy)ethanol by an azide group followed by the esterification reaction of the hydroxyl group with methacrylic anhydride. The copolymerization was carried out in an equivolumic mixture of H₂O and isopropanol at r.t. and initiated by a ω-bromoisobutyryl oligo PEO macroinitiator in the presence of various ligated copper(I)-based catalysts. In a last step, both polymer precursors were chemically linked by the Huisgen-1,3-dipolar cycloaddition in anhydrous THF at r.t. using CuBr complexed by 2,2′-bipyridine ligand as catalyst. Final material was characterized by the means of DSC and SEM, both attesting of a homogeneous distribution of the PCL crosslinkers and a highly porous structure in this new amphiphilic model conetworks.