Polymer network structure as revealed by small angle neutron scattering

Structural Properties of Covalently Crosslinked Gels as Probed by Scattering Techniques

This paper reviews some characteristic results obtained by scattering techniques in two sorts of swollen covalently crosslinked networks : neutral networks swollen by a good solvent and weakly ionized gels. For neutral networks swollen at saturation, the local conformation of the chains was found to be the same as in semi-dilute solutions, whereas some concentration inhomogeneities are observed at larger scale. Ionized gels are characterized by a peak of the structure factor and the absence of long range stationary concentration fluctuations at the concentration of preparation of the gels.

Dependence of Self-Assembled Peptide Hydrogel Network Structure on Local Fibril Nanostructure

Physically cross-linked, fibrillar hydrogel networks are formed by the self-assembly of β-hairpin peptide molecules with varying degrees of strand asymmetry. The peptide registry in the self-assembled state can be used as a design element to generate fibrils with twisting, nontwisting, or laminated morphology. The mass density of the networks varies significantly, and can be directly related to the local fibrillar morphology as evidenced by small angle neutron scattering (SANS) and in situ substantiation using cryogenic transmission electron microscopy (cryo-TEM) under identical concentrations and conditions. Similarly, the density of the network is dependent on changes in the peptide concentration. Bulk rheological properties of the hydrogels can be correlated to the fibrillar nanostructure, with the stiffer, laminated fibrils forming networks with a higher G' as compared to the flexible, singular fibrillar networks.