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

Abstract

By using free radical polymerization of (N-methacryloyloxyethyl-N′-4-picolyl)-urea (MAcPU) and N-acryloyl-L-leucine (AcLeu), an optically active copolymer, poly[(N-methacryloyloxyethyl-N′-4-picolyl)-urea-co-N-acryloyl-L-leucine], MAcPU-co-AcLeu (1.86:1 molar ratio) was prepared and subsequently functionalized at the pyridine-N with (1R/S)-(−/+)-10-camphorsulfonic acid (R/S-CSA) and at carboxyl group with (R)-(+)-α-ethylbenzylamine (R-EBA) or trans-4-stilbene methanol (t-StM). The structures, chemical composition and chiroptical activity of the monomers and the copolymers were characterized by spectral analysis (FTIR, ¹H (¹³C)-NMR, ¹H,¹H-COSY, UV/vis), thermal methods (TGA, DSC), fluorescence spectroscopy, atomic force microscopy, gel permeation chromatography and specific rotation measurements. Influence of the optical activity on modified copolymers suggested a good correlation between the experimental data obtained ( for AcLeu and MAcPU-co-AcLeu,  for (MAcPU-co-AcLeu)-R/S-CSA,  for (MAcPU-co-AcLeu)-R-EBA, and  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 amine in DMF solution was evaluated, more efficiently being 4,4′−dipyridyl (detection limit: 7.2 x 10^-6 mol/L).