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The number average molar mass is a way of determining the molecular mass of a polymer.Polymer molecules, even ones of the same type, come in different sizes (chain lengths, for linear polymers), so the average molecular mass will depend on the method of averaging.
The number-average molecular weight (M n) and weight-average molecular weight (M w) are most commonly reported. [28] [29] The ratio of these two values (M w / M n) is the dispersity (Đ), which is commonly used to express the width of the molecular weight distribution. [30]
The degree of polymerization, or DP, is the number of monomeric units in a macromolecule or polymer or oligomer molecule. [1] [2] [3]For a homopolymer, there is only one type of monomeric unit and the number-average degree of polymerization is given by ¯ ¯ = ¯, where ¯ is the number-average molecular weight and is the molecular weight of the monomer unit.
The molecular mass of a polymer differs from typical molecules, in that polymerization reactions produce a distribution of molecular weights and shapes. The distribution of molecular masses can be summarized by the number-average molecular weight, weight-average molecular weight, and polydispersity .
M n is the number-average molar mass (or molecular weight). ... To achieve any high molecular weight polymer, the fractional conversion must exceed 0.99, and the ...
Average molecular weight: ... Where N is the total number of polymer molecules present in the reaction. [14] Weight fraction distribution
Polymers are chainlike molecules that are made of the same repetition unit. With a few exceptions such as proteins, a polymer consists of a mix of molecules with different chain lengths. Therefore, average values are given for the molecular weight like the number average, the weight average or the viscosity average
A membrane osmometer is a device used to indirectly measure the number average molecular weight of a polymer sample. One chamber contains pure solvent and the other chamber contains a solution in which the solute is a polymer with an unknown M n {\displaystyle M_{n}} .