Temperature-controlled release of catechol dye in thermosensitive phenylboronate-containing copolymers: A quantitative study

The reversible complex formation between two phenylboronic acid bearing copolymers and the catechol dye Alizarin Red S (ARS) was studied by dialysis experiments coupled with UV-visible spectroscopy. The first copolymer based on N-isopropylacrylamide (NIPAM) is thermosensitive, whereas the second one based on N,N-dimethylacrylamide (DMAM) is not. The investigation resulted in the quantitative determination of the host-guest binding constants at two different temperatures at pH 7.4 in phosphate buffer. Above the phase transition temperature Tp of the thermosensitive copolymer, the binding constant decreases by a factor of 6, twice more than in the case of the non-thermosensitive copolymer. This behaviour is related to the coil-to-globule transition of NIPAM-based copolymer, which above Tp expels the dye marker. (C) 2010 Elsevier Ltd. All rights reserved.