Characterization of amphiphilic diblock copolymers synthesized by MADIX polymerization process

Abstract

We combined several analytical techniques (NMR, matrix assisted laser desorption ionization time-of-flight mass spectroscopy MALDI-TOE MS, GPC, functional analysis on the first block, liquid chromatography at the point of exclusion adsorption transition LC-PEAT, and capillary electrophoresis CE) to analyze and quantify the characteristics of homopolymer precursors and amphiphilic diblocks synthesized by controlled radical polymerization process (CRP). We present here a detailed quantitative characterization of amphiphilic diblock copolymers (poly(butyl acrylate)-poly(acrylic acid) or PBA-b-PAA, and poly(di(ethylene glycol) ethyl ether acrylate)-poly(acrylic acid) or PDEGA-&-PAA). The samples were synthesized in ethanol by macromolecular design via inter-exchange of xanthate (MADIX), a reversible addition fragmentation transfer (RAFT) polymerization process using xanthates as control agents. The analytical results have permitted a determination of the transfer constant of xanthate CXa (≈ 2.7 and 1.5 for respectively PB A and PDEGA) and the transfer constant to solvent Cs (≈ 6 × 10-4). In the final diblock products, homopolymer side products were characterized. The amount of hydrophobic homopolymer was quantified by a specially developed LCPEAT technique in critical conditions for PBA. The hydrophilic homopolymer h-PAA amount was determined by quantitative capillary electrophoresis CE experiments. These analytical approaches allowed the quantification of the side products in a CRP system as well as the improvement of the reaction conditions via a thorough knowledge of the reaction mechanism. © 2007 American Chemical Society.