Polymer, Vol.51, No.18, 4103-4109, 2010
Interactions of binary liquid mixtures with polysaccharides studied using multi-dimensional NMR relaxation time measurements
Nuclear magnetic resonance transverse T-2 relaxation time has proven to be a valuable parameter for characterizing liquid/polymer interactions. This measurement is applicable to many food, personal care, and cosmetic products that contain multi-component liquid mixtures. Here, we investigate the interactions of corn starch with water/glycerol mixtures of different weight compositions and explore liquid exchange dynamics; such a system is relevant to the personal care industry. We use a combination of chemical shift resolved H-1 T-2 relaxation measurements and corresponding two-dimensional T-2 relaxation exchange experiments using both a conventional experimental protocol and a modified method with the addition of NMR chemical shift selectivity. Two relaxation regimes were evident for the hydroxyl H-1 (found in both water and glycerol) whilst three relaxation regimes are evident for the aliphatic glycerol H-1 associated here with strongly bound, weakly bound, and free (bulk) liquid, respectively. At higher water contents preferential absorption of glycerol was evident. T-2-T-2 exchange maps with a range of storage times reveal molecular exchange rates between all three regimes due to self-diffusion. Rapid exchange of water between the bulk and bound locations was evident in the case of pure water. Exchange rates for hydroxyl H-1 was considerably reduced by the inclusion of glycerol. (C) 2010 Elsevier Ltd. All rights reserved.