weight-average molecular weight

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weight-average molecular weight:

see molecular weightmolecular weight,
weight of a molecule of a substance expressed in atomic mass units (amu). The molecular weight may be calculated from the molecular formula of the substance; it is the sum of the atomic weights of the atoms making up the molecule.
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Both number- and weight-average molecular weights increase linearly at [TEMPO]/[BPO] = 0.9, showing that polymerization is still controlled at this condition after the initial reaction period.
Figures 9 and 10 show the corresponding profiles for number-and weight-average molecular weights, respectively.
The maximum weight-average molecular weight of PLGA obtained in present work is 19,500 g/mol with the molar ratio of BuOH/Sn[(Oct).sub.2] being 1.7 (Sample 1 in Table 1 and Sample 7 in Table 2).
The low molecular weight polymers, usually below about 800 weight-average molecular weight, do not have enough length to intertwine with the other chains.(8, 9) The relationship of molecular weight to viscosity is a linear function up to that critical molecular weight; above that figure ([greater than]800), the classical viscosity effect varies as the 3.4 power of the molecular weight.
M (n,0) and M M(w,0) are the initial number-average and weight-average molecular weight.
Compared to linear polymers having similar molecular weights, the high-molecular-weight hyperbranched polyethylenes (weight-average molecular weight of about [10.sup.5] g/mol) were found to exhibit outstanding shear stability with almost zero shear degradation in the KO test, enabling the formulated lubricants for high-shear applications.
In general, this trend is consistent with the variation of weight-average molecular weight of these copolymers but against the variation trend of short-branch concentration for the C8 group.
(wt%) virgin PP 0.163 0.739 0.948 200 0 0.105 0.769 0.808 230 0 0.124 0.763 0.773 200 0.01% A1 0.110 0.773 0.791 200 0.01669 A2 0.161 0.751 0.808 230 0.01% Al 0.162 0.741 0.740 230 0.0166% A2 0.151 0.749 0.874 200 0.03% A1 0.147 0.751 0.791 200 0.055% A2 0.124 0.763 0.777 230 0.03% A1 0.194 0.717 0.683 230 0.055% A2 0.149 0.742 0.697 200 0.1% A1 0.223 0.717 0.745 200 0.166% A2 0.170 0.730 0.718 230 0.1% A1 0.128 0.743 0.621 230 0.166% A2 0.286 0.705 0.777 Figures 5 and 6 show the effect of peroxide type on the weight-average molecular weight at both reaction temperatures.
In accordance to the viscosity number [[eta]]--molecular weight M relationship, the weight-average molecular weight [M.sub.w] was calculated using data determined by light scattering of fractionated PA66 samples (1) [14].
Although the values of the weight-average molecular weights may be somehow underestimated (see the Molecular Characterization section), the dispersion normally observed in the values of both ultimate properties does not justify a more precise determination of the molecular weight of the polymers.