Speaker
Description
Polysaccharides are crucial structural polymers of life and display a diverse set of conformations, although the origins of these conformations are not fully understood. In this study, a high molecular weight pectin polysaccharide was investigated in binary water–glycerol mixtures using a complementary combination of molecular dynamics simulations, rheology, calorimetry, and neutron scattering. By systematically varying solvent quality, the polymer chain was observed to undergo a non-monotonic sequence of conformational transitions: flexible → extended → collapsed, accompanied by pronounced shifts in viscoelastic response. Simulations revealed molecularly adsorbed water accumulating within ca. 0.40 nm of the chain surface as the glycerol fraction increased, indicating water’s preferential association with the polymer. Elastic fixed window scans on IN13 (ILL, France) and quasi-elastic neutron scattering on IRIS (ISIS, UK) substantiated this observation. The emergence of such preferential solvation is proposed to result in a dynamically heterogeneous solvation state that is entropically unfavourable, thereby promoting compensatory swelling and collapse of the polysaccharide chain. Results connect solvation-shell composition to conformational bistability and rheological behaviour, offering fundamental insights of broad relevance to soft matter, food physics, and the rational design of adaptive biomaterials.
