Intrinsic viscosity
Intrinsic viscosity [ η ] {\displaystyle \left[\eta \right]} is a measure of a solute's contribution to the viscosity η {\displaystyle \eta } of a solution. If η 0 {\displaystyle \eta _{0}} is the viscosity in the absence of the solute, η {\displaystyle \eta } is (dynamic or kinematic) viscosity of the solution and ϕ {\displaystyle \phi } is the volume fraction of the solute in the solution, then intrinsic viscosity is defined as the dimensionless number [ η ] = lim ϕ → 0 η − η 0 η 0 ϕ {\displaystyle \left[\eta \right]=\lim _{\phi \rightarrow 0}{\frac {\eta -\eta _{0}}{\eta _{0}\phi }}} It should not be confused with inherent viscosity, which is the ratio of the natural logarithm of the relative viscosity to the mass concentration of the polymer.