Accession Number : AD0689848

Title :   EVALUATION OF MOLECULAR WEIGHT FROM EQUILIBRIUM SEDIMENTATION. PART II. DETERMINATION OF MOLECULAR WEIGHT DISTRIBUTION BY AN ITERATIVE SCHEME OF RELAXATION.

Descriptive Note : Summary rept. Feb 67-Nov 68,

Corporate Author : AIR FORCE MATERIALS LAB WRIGHT-PATTERSON AFB OHIO

Personal Author(s) : Gehatia,Matatiahu T. ; Wiff,Donald R.

Report Date : APR 1969

Pagination or Media Count : 51

Abstract : A new method has been developed to evaluate the molecular weight distribution (MWD) from a single Equilibrium-Sedimentation experiment. At first, such a distribution is characterized by a first approximation, then the experiment readings of concentration gradient along the ultracentrifugal cell are compared with corresponding values calculated from the approximate MWD. With help of an iterative scheme based upon a method of Modified Relaxation an improved distribution curve can be calculated. This method has been easily adjusted to the limitations of an IBM 7094 computer. The success of such a calculation depends upon the width of intervals between the chosen fractions and is more immune against individual errors accompanying experimental readings. With help of this method, the MWD of polybenzimidazole in DMAC has been determined. The average error between experimental concentration gradient values and the one calculated from the obtained distribution was less than 0.3%. (Author)

Descriptors :   (*POLYMERS, *MOLECULAR WEIGHT), NUMERICAL ANALYSIS, SEDIMENTATION, SOLUTIONS(MIXTURES), DIFFUSION, CONCENTRATION(CHEMISTRY), BENZIMIDAZOLES

Subject Categories : Plastics
      Atomic and Molecular Physics and Spectroscopy

Distribution Statement : APPROVED FOR PUBLIC RELEASE