Seeking help with molecular weight determination
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This post was last edited by ljtjbx on 2015-11-25 at 14:01. The number-average molecular weight of the produced PMMA (polymethyl methacrylate) was 370,000. But the average molecular weight is 6350. I would like to ask how the 6350 data is calculated.
Average molecular weight? Aren’t there three types of molecular weights: number average, weight average, and viscosity average?
There is also the Z-average molecular weight. If two molecular weights are known, can the other two molecular weights be calculated? That place can issue a molecular weight identification report. Thank you
It’s not possible; although number-average, weight-average, and Z-average are all types of statistical molecular weights, their influence by molecules of different molecular weights differs vastly. Generally speaking, the low-molecular and ultra-low-molecular-weight fractions have a significant impact on the logarithmic mean weight, a slight impact on the weight average, and almost no impact on the Z-average ； Changes in the polymer and ultra-high molecular weight fractions have no effect on the logarithmic mean, have a slight effect on the weight average, and have a significant effect on the Z-average.
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I inquired, and Changzhou University is fine. Are there any netizens from Changzhou University?