Critical Concentration c* log7。 NB.235>10 so doubling concentration increases viscosity by ove an order of magnitude! slope =1.5 log c The zero-shear-rate viscosity of a polymer solution versus polymer concentration,showing the critical overlap concentration c. Intrinsic viscosity [n]=KM K and a are constants a varies from 0.5 for a random coil to 2 for a rigid rod Highly branched polymers When highly branched polymers are sheared. they too unwind,but they cannot form very long strings because of branching.Thus they do not give 'stringy liquids.' 55 Critical Concentration c* logηo log c Intrinsic viscosity [ ] η = KMα K and α are constants α varies from 0.5 for a random coil to 2 for a rigid rod Highly branched polymers When highly branched polymers are sheared, they too unwind, but they cannot form very long strings because of branching. Thus they do not give ‘stringy liquids.’