화학공학소재연구정보센터
Journal of Physical Chemistry B, Vol.116, No.39, 11953-11958, 2012
H-1 and H-2 NMR Spin-Lattice Relaxation Probing Water: PEG Molecular Dynamics in Solution
Nuclear magnetic resonance spin lattice relaxation times (T-1) measurements were performed in aqueous solutions of poly(ethylene glycol) (PEG) of 6000 Da molecular mass to study the dynamical relation between PEG and water molecules at different solute concentrations. H-1-T-1 experiments were carried on at a low magnetic field in the time domain (20 MHz) and at a high field (400 MHz) to obtain spectral resolution. Two contributing components were identified in each proton system, PEG and water, presenting values of T-1 with very different orders of magnitude. The approximate matching between the shorter H-1-T-1 values associated with water and PEG has lead us to conclude that there exists a network of interactions (hydrogen bonds) between the solute and the solvent, which results in the presence of an ordered and dehydrated structure of PEG folded or self-assembled in equilibrium with a more flexible monomer structure. Dynamic light scattering results were consistent with the formation of PEG aggregates, showing a mean size between 40 and 100 nm.