The number average molecular weight is usually smaller than the weight average molecular weight. The ratio of weight and number molecular weight is called the polydispersity index. It is a measure for the broadness of a molecular weight distribution of a polymer. Number average molecular weight: Mn The number average molecular weight is the statistical average molecular weight of all the polymer chains in the sample, and is defined by: Mn = SNiMi SNi where Miis the molecular weight of a chain and Niis the number of chains of that molecular weight. Mn can be predicted by polymerization mechanisms and is mea-. Determining the weight-average molecular weight or the number-average molecular weight is a part of any polymer characterization. Degree of polymerization The smallest repeatable unit in a polymer molecule is the mer unit (monomer).
Number average molecular weight of polymer unitsThis section should strictly be called “Polymer molecular mass”, but in polymer the most relevant average depends on the property being investigated: for example, The number average molecular weight is defined as the total weight of. where X is the degree of polymerization, the number of repeat units in the chain. • The molecular weight of a copolymer is based on a weighted average of the. The HDPE molecules, for example, are all long carbon chains, but the Mn, the number average molecular weight, is calculated from the mole. Degree of Polymerization. The degree of polymerization (DP) in a polymer molecule is the number, n, of repeating units in the polymer chain. factorytakayama.net Looking at Equation , M c ¯ can only be obtained when the values of the number-average molecular weight of the polymer before crosslinking (M n ¯), the. The mass average molar mass (often loosely termed weight average molar mass ) is another way of describing the molar mass of a polymer. The ratio of the mass average to the number average is called the p, in step-growth polymerization as per Carothers' equation. The number average molecular weight is the total weight of the sample divided by the First find the total weight of each type (or weight) of polymer. For example, there are 13 molecules with a weight of , so the total weight of. It is a way of determining the molecular mass of a polymer. For example, we can use the number average molecular weight which is based. Define the following terms: monomer, polymer, weight-average molecular weight and These repetitive units were originally the monomer molecules.
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