Neutron Scattering Studies of the Structure of a Polyelectrolyte Globule in a Water−Acetone Mixture

Abstract

The polycationic polyelectrolyte poly(methacryloylethyltrimethylammonium methyl sulfate) (PMETMMS) of high molecular weight (ca. 26 × 106 g mol-1) in dilute solutions with acetone−water mixtures displays a coil−globule transition above a certain threshold of acetone. SANS observations of this system indicate that the collapsed state of this molecule consists of a sequence of dense spheres with smooth surfaces connected by regions of loose polymer. The radius of the spheres, 28 nm, is smaller than either the hydrodynamic radius (RH = 39 nm) or the radius of gyration (RG = 42 nm). The number of such collapsed regions is small (3−4), the volume fraction of polymer inside them being about 8%.