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What differences in the final properties have a monodisperse and a polydisperse polymer?
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Albert Moody
What differences in the final properties have a monodisperse and a polydisperse polymer?
Polydispersity Index is nothing but the ratio of Weight average molecular weight to number average molecular weight. The weight average MW is always higher than Number average MW and hence the ratio starts from 1.
This dispersity index measures the deviation from the uniformity of dispersion. For example if the weight distribution is uniform then the ratio is 1. 1 to 1.1 it is considered to be narrow distribution, 1–2 is moderate distribution and more than 2 is noted as broad distribution
Polydispersity Index is nothing but the ratio of Weight average molecular weight to number average molecular weight. The weight average MW is always higher than Number average MW and hence the ratio starts from 1.
This dispersity index measures the deviation from the uniformity of dispersion. For example if the weight distribution is uniform then the ratio is 1. 1 to 1.1 it is considered to be narrow distribution, 1–2 is moderate distribution and more than 2 is noted as broad distribution
The answer is in the rheology curves… A monodisperse (really narrow molecular weight distribution) polymer will have a flat curve ( complex viscosity, elastic modulus G’ both vs. temperature or shear rate) a.k.a Newtonian plateau till a certain crossover point where it will dramatically drop down (where elastic modulus G’ becomes lower than loss modulus G”). A polydisperse polymer will have a tilting down curve, slightly higher than an equivalent narrow distribution material alt low shear (contribution of long chains) that progressively drops as shear rate increases (short chains acting as an internal plasticizer), As the shear rate increases it will reach the crossover point that will occur at lower shear rate but in a less dramatic way than an equivalent mono or narrow molecular weight distribution material, after which G’ will continue to drop but less than the latter material. In conclusion, a narrow MW material will be harder to process and it will give a mechanically stronger, but suddenly failing final product. A wide MW distribution polymer will process easily and will give a less performing but more forgiving final product. Narrow MW polymers are better for rods, wide ones for films.. This is a quick summary of a complex and very wide topic….
The answer is in the rheology curves… A monodisperse (really narrow molecular weight distribution) polymer will have a flat curve ( complex viscosity, elastic modulus G’ both vs. temperature or shear rate) a.k.a Newtonian plateau till a certain crossover point where it will dramatically drop down (where elastic modulus G’ becomes lower than loss modulus G”). A polydisperse polymer will have a tilting down curve, slightly higher than an equivalent narrow distribution material alt low shear (contribution of long chains) that progressively drops as shear rate increases (short chains acting as an internal plasticizer), As the shear rate increases it will reach the crossover point that will occur at lower shear rate but in a less dramatic way than an equivalent mono or narrow molecular weight distribution material, after which G’ will continue to drop but less than the latter material. In conclusion, a narrow MW material will be harder to process and it will give a mechanically stronger, but suddenly failing final product. A wide MW distribution polymer will process easily and will give a less performing but more forgiving final product. Narrow MW polymers are better for rods, wide ones for films.. This is a quick summary of a complex and very wide topic….
Polymers are a huge class of materials, plastics and thermosets, films and fibers, natural and man-made. It is impossible to answer the question without more specifics.
Polymers are a huge class of materials, plastics and thermosets, films and fibers, natural and man-made. It is impossible to answer the question without more specifics.
Polymer is a common word which describes a huge class of materials with various properties. The defining property of a particular polymer depends upon its type.
For a material to be called a polymer, it should consist of long chain molecules which are made up of several small repeating units called monomers. This is basic definition of a polymer material.
Polymer is a common word which describes a huge class of materials with various properties. The defining property of a particular polymer depends upon its type.
For a material to be called a polymer, it should consist of long chain molecules which are made up of several small repeating units called monomers. This is basic definition of a polymer material.
Atactic polymers are polymers where the side chain is arranged randomly along the backbone chain .
In isotactic polymers the the chain is arranged on one side of the backbone chain.
Syndiotactic polymers are polymers where the side chain is arranged alternatively on both sides of the backbone chain.
Classic example is Polypropylene. For more look for atactic , syndiotactic and isotactic Polypropylene. Position of side chain have a major role with respect to properties of polymers.
Atactic polymers are polymers where the side chain is arranged randomly along the backbone chain .
In isotactic polymers the the chain is arranged on one side of the backbone chain.
Syndiotactic polymers are polymers where the side chain is arranged alternatively on both sides of the backbone chain.
Classic example is Polypropylene. For more look for atactic , syndiotactic and isotactic Polypropylene. Position of side chain have a major role with respect to properties of polymers.
Because the properties are different, we have different polymers. Substances are differentiate by differences in their properties. If polymers do not have different properties, we will have only one polymer.
Because the properties are different, we have different polymers. Substances are differentiate by differences in their properties. If polymers do not have different properties, we will have only one polymer.
The polydispersity index (PI) is a measure of the heterogeneity of a sample based on size. Polydispersity can occur due to size distribution in a sample or agglomeration or aggregation of the sample during isolation or analysis.
The polydispersity index (PI) is a measure of the heterogeneity of a sample based on size. Polydispersity can occur due to size distribution in a sample or agglomeration or aggregation of the sample during isolation or analysis.
Polydispersity Index is nothing but the ratio of Weight average molecular weight to number average molecular weight. The weight average MW is always higher than Number average MW and hence the ratio starts from 1.
This dispersity index measures the deviation from the uniformity of dispersion. For example if the weight distribution is uniform then the ratio is 1. 1 to 1.1 it is considered to be narrow distribution, 1–2 is moderate distribution and more than 2 is noted as broad distribution
Polydispersity Index is nothing but the ratio of Weight average molecular weight to number average molecular weight. The weight average MW is always higher than Number average MW and hence the ratio starts from 1.
This dispersity index measures the deviation from the uniformity of dispersion. For example if the weight distribution is uniform then the ratio is 1. 1 to 1.1 it is considered to be narrow distribution, 1–2 is moderate distribution and more than 2 is noted as broad distribution
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The answer is in the rheology curves… A monodisperse (really narrow molecular weight distribution) polymer will have a flat curve ( complex viscosity, elastic modulus G’ both vs. temperature or shear rate) a.k.a Newtonian plateau till a certain crossover point where it will dramatically drop down (where elastic modulus G’ becomes lower than loss modulus G”). A polydisperse polymer will have a tilting down curve, slightly higher than an equivalent narrow distribution material alt low shear (contribution of long chains) that progressively drops as shear rate increases (short chains acting as an internal plasticizer), As the shear rate increases it will reach the crossover point that will occur at lower shear rate but in a less dramatic way than an equivalent mono or narrow molecular weight distribution material, after which G’ will continue to drop but less than the latter material. In conclusion, a narrow MW material will be harder to process and it will give a mechanically stronger, but suddenly failing final product. A wide MW distribution polymer will process easily and will give a less performing but more forgiving final product. Narrow MW polymers are better for rods, wide ones for films.. This is a quick summary of a complex and very wide topic….
The answer is in the rheology curves… A monodisperse (really narrow molecular weight distribution) polymer will have a flat curve ( complex viscosity, elastic modulus G’ both vs. temperature or shear rate) a.k.a Newtonian plateau till a certain crossover point where it will dramatically drop down (where elastic modulus G’ becomes lower than loss modulus G”). A polydisperse polymer will have a tilting down curve, slightly higher than an equivalent narrow distribution material alt low shear (contribution of long chains) that progressively drops as shear rate increases (short chains acting as an internal plasticizer), As the shear rate increases it will reach the crossover point that will occur at lower shear rate but in a less dramatic way than an equivalent mono or narrow molecular weight distribution material, after which G’ will continue to drop but less than the latter material. In conclusion, a narrow MW material will be harder to process and it will give a mechanically stronger, but suddenly failing final product. A wide MW distribution polymer will process easily and will give a less performing but more forgiving final product. Narrow MW polymers are better for rods, wide ones for films.. This is a quick summary of a complex and very wide topic….
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Polymers are a huge class of materials, plastics and thermosets, films and fibers, natural and man-made. It is impossible to answer the question without more specifics.
Polymers are a huge class of materials, plastics and thermosets, films and fibers, natural and man-made. It is impossible to answer the question without more specifics.
More
VOTE
Polymer is a common word which describes a huge class of materials with various properties. The defining property of a particular polymer depends upon its type.
For a material to be called a polymer, it should consist of long chain molecules which are made up of several small repeating units called monomers. This is basic definition of a polymer material.
Polymer is a common word which describes a huge class of materials with various properties. The defining property of a particular polymer depends upon its type.
For a material to be called a polymer, it should consist of long chain molecules which are made up of several small repeating units called monomers. This is basic definition of a polymer material.
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The biggest difference that comes to mind is melt viscosity.
A monodisperse polymer (Dispersity index of 1.1 or less) will have little to no melt viscosity. This can make it very difficult to process.
A polydisperse polymer will have more melt viscosity and can be processed through techniques like extrusion.
I'm sure there are more.
The biggest difference that comes to mind is melt viscosity.
A monodisperse polymer (Dispersity index of 1.1 or less) will have little to no melt viscosity. This can make it very difficult to process.
A polydisperse polymer will have more melt viscosity and can be processed through techniques like extrusion.
I'm sure there are more.
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Atactic polymers are polymers where the side chain is arranged randomly along the backbone chain .
In isotactic polymers the the chain is arranged on one side of the backbone chain.
Syndiotactic polymers are polymers where the side chain is arranged alternatively on both sides of the backbone chain.
Classic example is Polypropylene. For more look for atactic , syndiotactic and isotactic Polypropylene. Position of side chain have a major role with respect to properties of polymers.
Atactic polymers are polymers where the side chain is arranged randomly along the backbone chain .
In isotactic polymers the the chain is arranged on one side of the backbone chain.
Syndiotactic polymers are polymers where the side chain is arranged alternatively on both sides of the backbone chain.
Classic example is Polypropylene. For more look for atactic , syndiotactic and isotactic Polypropylene. Position of side chain have a major role with respect to properties of polymers.
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Because the properties are different, we have different polymers. Substances are differentiate by differences in their properties. If polymers do not have different properties, we will have only one polymer.
Because the properties are different, we have different polymers. Substances are differentiate by differences in their properties. If polymers do not have different properties, we will have only one polymer.
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The polydispersity index (PI) is a measure of the heterogeneity of a sample based on size. Polydispersity can occur due to size distribution in a sample or agglomeration or aggregation of the sample during isolation or analysis.
The polydispersity index (PI) is a measure of the heterogeneity of a sample based on size. Polydispersity can occur due to size distribution in a sample or agglomeration or aggregation of the sample during isolation or analysis.
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