What is number average and weight average molecular weight of polymer?
The distribution of molecular weights in a polymer sample is often described by the ratio of the weight average molecular weight to the number average molecular weight. In this case the ratio is 531,600/500,000 = 1.063.
…
| Number of Molecules | Mass of each Molecule |
|---|---|
| 8 | 650,000 |
| 10 | 600,000 |
| 13 | 550,000 |
| 20 | 500,000 |
How do you find the molecular weight of a polymer?
The Number Average Molecular Weight is the total weight of the polymer molecules divided by the total number of polymer molecules.
Which method used for weight average molecular weight?
Osmometry is applied to determine number average of molecular weight (Mn).
Why do we take average molecular weight of polymers?
Unlike simpler pure compounds, most polymers are not composed of identical molecules. The HDPE molecules, for example, are all long carbon chains, but the lengths may vary by thousands of monomer units. Because of this, polymer molecular weights are usually given as averages.
What is MN and Mw in polymer?
Mn is the number averaged MW, and Mw is the weight averaged MW. The midpoint of the distribution in terms of the number of molecules is Mw. The third moment, Mz, has more weighting with regards to higher MWs. The Mw:Mn ratio is termed as polydispersity, and is used for describing the distribution width.
What are the different types of molecular weight of a polymer?
Molecular Weight (Polymers)
- Oligomer.
- Ligand.
- Copolymer.
- Nanoparticle.
- Molar Mass Distribution.
- [Alpha]
- Polydispersity.
- Polymer Chain.
How can molecular weight of a polymer be measured experimentally?
(1) MW can be measured using many different methods including gel permeation chromatography (GPC), osmometry, light scattering, viscometry, cryoscopy, ebulliometry, ultracentrifugation, mass spectrometry, and end-group analysis.
How do you calculate the average molecular weight from the degree of polymerization?
Divide the molecular weight of the polymer by the molecular weight of the monomer unit to calculate the degree of polymerization. If the molecular mass of tetrafluoroethylene is 120,000, its degree of polymerization is 120,000 / 100 = 1,200.
Which one is best method for molecular mass determination of polymer?
Osmotic pressure method
(A) : Osmotic pressure method is the most suitable method to determine the number average molecular masses of polymers.
Which apparatus is used in determination of molecular weight of the polymer?
Gel permeation chromatography is used to determine the number average molecular weight, weight average molecular weight, and polydispersity.
How is Mw polymer measured?
How do you calculate Mn Mw and polymer?
Polymer distributions are typically characterized by Mn and Mw, which are calculated from the formula: Mn = (NiMi)/Ni and Mw = (NiMi2)/NiMi Ni and Mi are the abundance and mass of the ith oligomer, respectively.
What is weight average molecular weight?
N. The number average molecular weight is defined as the total weight of polymer divided by the total number of molecules.
Which method is the best method for determining the molecular weight of polymers?
How do you calculate DP of a polymer?
What is weight average molecular weight derive it’s equation?
The formula to determine ‘weight average molecular weight’ of polymers is, (Mn)=∑n1m1∑n1m12. where, n1:Number of molecules. m1:Molecular mass.
What technique can measure molecular weight directly?
Molecular weight, as well as molecular structure, of small molecules can be determined using mass spectrometry. Using a direct infusion method, samples can be introduced directly to the detector to confirm the molecular weight of a known material, or provide structural characterization of an unknown.
What is Mw and Mn of polymer?
What is the formula to find average weight?
To find a weighted average, multiply each number by its weight, then add the results. If the weights don’t add up to one, find the sum of all the variables multiplied by their weight, then divide by the sum of the weights.
How is molecular weight of polymer determined by viscosity method?
Viscometry or viscosity method was one of the first methods used for determining the MW of polymers. In this method, the viscosity of polymer solution is measured, and the simplest method used is capillary viscometry by using the Ubbelohde U-tube viscometer.
What is the relation between DP and molecular weight?
The degree of polymerization (DP or Xn) is defined as the number of monomer units in the polymer. It is calculated as the ratio of molecular weight of a polymer and molecular weight of the repeat unit. Number average DP and weight average DP are the two main types used for measuring the DP.
How do you calculate average molecular weight?
The average molecular weight is determined by summing the weights of all the chains and then dividing by the total number of chains. The average molecular weight is an important method of characterizing polymers.
What is the weight average molecular weight?
The average molecular weight is determined by summing the weights of all the chains and then dividing by the total number of chains. The average molecular weight is an important method of characterizing polymers. The three ways to represent average molecular weight is: • number average molecular weight, M.
Why is weighted average used?
In a weighted average, each data point value is multiplied by the assigned weight, which is then summed and divided by the number of data points. For this reason, a weighted average can improve the data’s accuracy. Stock investors use a weighted average to track the cost basis of shares bought at varying times.
What is the weighted average method?
Weighted average is a calculation that takes into account the varying degrees of importance of the numbers in a data set. In calculating a weighted average, each number in the data set is multiplied by a predetermined weight before the final calculation is made.