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Molecular Weight of Polymers
Published in Charles E. Carraher, Carraher's Polymer Chemistry, 2017
Staudinger showed that the intrinsic viscosity of a solution (η) or LVN is related to the molecular weight of the polymer. The present form of this relationship was developed by Mark–Houwink (and is known as the Mark–Houwink equation) in which the proportionality constant K is characteristic of the polymer and the solvent and the exponential a is a function of the shape of the polymer in a solution. For theta solvents, the value of a is 0.5. This value, which is actually a measure of the interaction of the solvent and polymer, increases as the coil expands and the value is between 1.8 and 2.0 for rigid polymer chains extended to their full contour length and 0 for spheres. When a is 1.0, the Mark–Houwink equation 3.31 becomes the Staudinger viscosity equation: LVN=KM¯a
Viscometers–Laboratory
Published in Béla G. Lipták, Analytical Instrumentation, 2018
The Mark-Houwink equation expresses the relationship between intrinsic viscosity and molecular weight: ) [μI]=KMwa or, in logarithmic form: ) log [μI]=logK+alogMw
Molecular Characterization
Published in Rudolf Puffr, Vladimír Kubánek, Lactam-Based Polyamides, 2019
As has been stated above, molecular weights can be derived from viscosity data. For molecules of one type (e.g., linear) of a given polymer, intrinsic viscosity and molecular weight are related by the Mark-Houwink equation [η]=KMa
Plant mediated green synthesis and nanoencapsulation of MgO nanoparticle from Calotropis gigantea: Characterisation and kinetic release studies
Published in Inorganic and Nano-Metal Chemistry, 2018
Yiik Siang Hii, Jaison Jeevanandam, Yen San Chan
From Mark-Houwink equation, it can be seen that intrinsic viscosity is directly related to molecular weight of polymer. Consequently, a higher intrinsic viscosity results in higher viscosity of the organic phase and instigates a better distribution of the drug in the matrix. Conversely, lowering the viscosity of the organic phase allows drugs to come close to the surface during particles formation and dissolve in the surrounding aqueous medium, resulting in lower drug content.[18] To conclude, Eudragit L as the polymer have a better drug entrapment efficiency, drug loading percent and yield.