Quantifying the influence of ionic liquid on the phase behaviour of a biomedical thermoresponsive polymer: A biophysical experimental approach

摘要

Thermoresponsive polymers (TRPs) are known to exhibit changes in conformational states, with a change in the solution temperature. Obviously, temperature is the key factor that responds to the conformational transition behavior of TRPs. Among various TRPs, poly (N-vinylcaprolactam) (PVCL) is a suitable amphiphilic polymer for the study of conformational changes due to its compatible behavior with various additives. In the current study, the effect of 1-allyl-3-methylimidazolium bromide ([Amim] [Br]) on phase transition behavior of PVCL aqueous solution was studied. In order to investigate the alterations on phase behavior of PVCL in [Amim] [Br], various biophysical techniques such as ultraviolet-visible absorption spectroscopy, steady-state fluorescence spectroscopy, Fourier transform infrared (FTIR) spectroscopy, thermal fluorescence spectroscopy, dynamic light scattering (DLS) and differential scanning calorimetry (DSC) were used. Our experimental results explicitly elucidated that [Amim] [Br] increases the lower critical solution temperature (LCST) of PVCL with increasing the concentration of ionic liquid (IL). The main rationale observed is attributed to the IL interaction affinity depending on its cationic and anionic part's affinity towards water molecules that are strongly attached to the bonds in pure PVCL and become more attracted to the IL and thus resulted in the facilitation of hydrated form of PVCL.