In both biological and engineered systems, polysaccharides
offer
a means of establishing structural stiffness without altering the
availability of water. Notable examples include the extracellular
matrix of prokaryotes and eukaryotes, artificial skin grafts, drug
delivery materials, and gels for water harvesting. Proper design and
modeling of these systems require detailed understanding of the behavior
of water confined in pores narrower than about 1 nm. We use molecular
dynamics simulations to investigate the properties of water in solutions
and gels of the polysaccharide alginate as a function of the water
content and polymer cross-linking. We find that a detailed understanding
of the nanoscale dynamics of water in alginate solutions and gels
requires consideration of the discrete nature of water. However, we
also find that the trends in tortuosity, permeability, dielectric
constant, and shear viscosity can be adequately represented using
the “core–shell” conceptual model that considers
the confined fluid as a continuum.