Viscometry of PLA

The molecular characterization of PLA depends on the accurate knowledge of its fundamental properties. These include such parameters as Mark-Houwink constants that relate intrinsic viscosity to molecular weights, theta-condition front factors (K ) used to calculate single chain properties, and characteristic ratios (Coo) that give an indication of the bonding structure of polymers. 

Different definitions of the mean squared monomer step length 

FIGURE 10.1 Stockmayer-Fixman plots, reconstructed from published Mark-Houwink parameters, illustrating inconsistencies in the PLA literature. Rather than the wide range of values exhibited, the y-axis intercepts should be a common value equal to K . 

Different expansion factor models for correcting data obtained in good solvents to Q conditions, or neglecting of such correction altogether [4] 

Different assumed values for the viscosity function F (or Flory constant) used to relate intrinsic viscosities to molecular dimensions in solution 

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