Entanglement coupling in porcine stomach mucin

We present data from small angle neutron scattering (SANS) on the polyelectrolyte side chain liquid crystalline phases of porcine stomach mucin. There is a polydomain nematic phase at concentrations above the point of brush overlap. Also, the proteoglycans were seen to orient under the influence of a magnetic field at concentrations below which the brushes do not extensively overlap. The field can be used to investigate the nature of the entanglement coupling between the molecules. The structure factor peak scales as c(1/3) across the complete concentration range, implying liquidlike behavior (0.4-680 mg/mL). The rheological data present evidence for shear thinning with four regimes: dilute, semidilute, entangled polydomain liquid crystalline, and entangled liquid crystalline. The length and cross-sectional radius of the polymeric brushes could be measured with SANS. Static light scattering and SANS provide evidence for the changes in osmotic compressibility between dilute, semidilute, and entangled brush phases.