Copolymers based on N-acryloyl-L-leucine and urea methacrylate with pyridine moieties

Abstract

By using free radical polymerization of 2-{[((4-pyridinylmethyl)-amino)carbonyl]amino}ethyl methacrylate (MAcPU) and N-acryloyl-L-leucine (AcLeu), an optically active copolymer, poly{2-{[((4-pyridinylmethyl)amino)-carbonyl]amino}ethyl methacrylate-co-N-acryloyl-L-leucine}, MAcPU-co-AcLeu (1.86:1 mole ratio), was prepared and subsequently functionalized at the pyridine-N with (1R/S)-(±)-10-camphorsulfonic acid (R/S-CSA) and at the carboxyl group with (R)-(+)-α-ethylbenzylamine (R-EBA) or trans-4-stilbenemethanol (t-StM). The structures, chemical compositions and chiroptical activities of the monomers and the copolymers were characterized by spectral analysis (FTIR, 1H- and 13C-NMR, 1H,1H-COSY and UV-Vis), thermal methods (TGA and DSC), fluorescence spectroscopy, gel permeation chromatography and specific rotation measurements. The influence of the optical activity of the monomer and modifier on the modified copolymers suggested a good correlation between the experimental data obtained ( [α]23589 =+12.5° for AcLeu and MAcPU-co-AcLeu, [α]23589 =0° / +27.5° for (MAcPU-co-AcLeu)-R/S-CSA, [α]23589 =+25° for (MAcPU-co-AcLeu)-R-EBA, and [α]23589 =0° for (MAcPU-co-AcLeu)-St). In addition, the photobehavior of the stilbene copolymer (MAcPU-co-AcLeu)-St in film was investigated by UV-Vis spectroscopy. The fluorescence quenching of the stilbene species in the presence of aliphatic/aromatic amines in DMF solution was evaluated, more efficient being 4,4′-dipyridyl (detection limit: 7.2×10-6 mol L-1).