Poly(ethylene glycol)s 2000–8000 in water may be planar: A small-angle neutron scattering (SANS) structure study

Poly(ethylene glycol)s of all molecular weights are highly soluble in water. Small-Angle Neutron Scattering (SANS) data has been collected on buffered ionic D2O solutions of PEGs of nominal molecular weights 2000, 4000, and 8000 Da at a low concentration of 0.5% (w/v). The radii of gyration Rg vary as approximately Mw0.5, which is consistent with both a Gaussian chain and a flat plate. Numerous types of experiments indicate flaws in the interpretation as a Gaussian chain. When the alternative interpretation is used, the structures in these dilute solutions are found to have a constant area stoichiometry of 1:1 water:–CH2CH2O– and are consistent with the data when monomeric molecules are plates of packed chains one chain thick.