Delving the osmolyte-induced modulation of the temperature-responsive behavior of PNIPAM-b-PACMO

Abstract

Osmolytes are tiny organic compounds that alter the behavior of macromolecules and are ubiquitous in biological systems. The effects of osmolytes, such as urea and TMAO, and their mixture on the hydrated state and hydrophobic association behavior of the PNIPAM-b-PACMO copolymer have been thoroughly investigated by employing UV-visible spectroscopy, fluorescence spectroscopy, dynamic light scattering (DLS), and Fourier transform infrared spectroscopy (FTIR). Both urea and TMAO affect the phase transition temperature of the diblock copolymer, with urea typically lowering the LCST and TMAO producing more subtle changes depending on the concentrations of osmolytes. Later, the lower critical solution temperature (LCST) values of the block copolymer in the osmolytes and their mixtures have also obtained by temperature-dependence of DLS as the functions of the concentrations of the additives. These results reveal that the LCST values of copolymer decrease as the concentration of additives increase. The study highlights the molecular interactions, both direct and indirect, that contribute to these changes, underscoring the role of co-solutes in stabilizing the dehydrated state of the copolymer. This work could also pave the way for new approaches in the synthesis of PNIPAM-based devices and drug delivery systems.