Determination of the Polymer Coil Dimensions from the Intrinsic Viscosity

Abstract

The concentration of a polymer in solution yields no information on how much of the solution volume is filled with polymer coils. Depending on the influence parameters described in the previous chapters, the expansion of a polymer coil in solution can increase or decrease. Even at polymer concentrations that are seemingly relatively low, for example c<0.1 %, polymer coils with large intrinsic viscosities (in this case [η]>2500 ml g^-1) completely fill the solution volume. Although the intrinsic viscosity contains this information, some experience is needed to estimate the percentage of solution volume filled with polymers given the intrinsic viscosity. Thus in the following the calculation of the volume V_coil and diameter d of a single polymer coil from the intrinsic viscosity is shown. These dimensions allow for the calculation of the volume demand of the polymer in solution, especially the concentration where 100% of the solution volume is filled. This concentration is denoted in the next section as the critical concentration c*. Since nearly all technical applications of polymer solutions require concentrations above c*, viscosimetry permits an easy determination of the required minimum concentration of the polymer via the intrinsic viscosity.