The molecular weight of a polymer is directly related to its properties. As the molecular weight increases, mechanical properties generally increase. Every polymer has an ideal molecular weight at which the balance of different properties (such as processability, strength, brittleness etc.) is optimized.
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Why must average molecular weights be used for polymers rather than exact molecular weight as is done for the small molecules based on their structural formula?
The number average molecular weight takes into account all the polymeric molecules in the averaging process while the weight average molecular weight is biased towards higher MW macro molecules counting their contribution foremost in the averaging process while putting aside the smaller MW poly molecules.
What is molecular weight and how it affects the properties of a polymer?
1.4. A polymer’s molecular weight is the sum of the atomic weights of the individual atoms that comprise a molecule. It indicates the average length of the bulk resin’s polymer chains. All polymer molecules of a particular grade do not have the exact same molecular weight.
What is used to determine molecular weight of polymers?
Therefore, in order to determine the molecular weight and molecular weight distribution of a polymer, one of the most widely applied methods is gel-permeation chromatography. Gel permeation chromatography (GPC) is a term used for when the separation technique size exclusion chromatography (SEC) is applied to polymers.
What is molecular weight used for?
Molecular weight is a measure of the sum of the atomic weight values of the atoms in a molecule. Molecular weight is used in chemistry to determine stoichiometry in chemical reactions and equations.
Why molecular weight of a polymer is so important for a fiber forming polymer?
Molecular weight is important in polymer chemistry because it has an effect on the chemical properties. A higher molecular weight increases the resistance the polymer has to impact. This is because when there are more polymer bonds to break, it takes more energy to overcome the resistance of the polymer.
How do you control the molecular weight of a polymer during material or polymer production?
- Increase the amount of initiator relative to monomer (i.e. double or triple the amount).
- Use a chain transfer agent such as a thiol or mercaptan (R-S-H).
What do you understand by molecular weight and degree of polymerization of polymer?
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 does molecular weight influence the polymer solubility?
As the molecular weight of the solute increases, the value of ฮฉ decreases, and, as a result the entropic driving forces are diminished for dissolution of polymers. As a consequence, polymer solubility depends strongly on the enthalpic interaction between the polymer and the solvent.
How does molecular weight affect properties?
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.
Which one is best method for molecular mass determination of polymer?
(A) : Osmotic pressure method is the most suitable method to determine the number average molecular masses of polymers.
Which method for determination of molecular weight of polymer is convenient and least complicated?
The most accurate method for determine absolute molecular mass of a polymer is vapor pressure osmometry (VPO).
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.
Why is the molecular weight of a protein important?
Protein molecular weight is a key parameter to confirm, as the primary structure is the most foundational level of protein structure. Developing a robust understanding of the unmodified protein molecular weight can assist in initial assessments of the biomolecule’s functionality.
What is molecular weight explain with example?
The sum of the atomic masses of all atoms in a molecule, based on a scale in which the atomic masses of hydrogen, carbon, nitrogen, and oxygen are 1, 12, 14, and 16, respectively. For example, the molecular weight of water, which has two atoms of hydrogen and one atom of oxygen, is 18 (i.e., 2 + 16).
How does molecular weight affect crystallinity?
Molecular weight With the increase in molecular weight of the polymer, the degree of crystallinity increases due to a large number of entanglement of the chain which restricts the growth of a crystallite.
How do you increase the molecular weight of a polymer?
Cross-linking can be thought of as reducing the number of chain ends and, effectively, increasing the molecular weight of a polymer system [61]. In general, cross-linking will increase the strength of material [62].
What is the importance of degree of polymerization?
The degree of polymerization has a dramatic effect on the mechanical properties of a polymer. As chain length increases, mechanical properties such as ductility, tensile strength, and hardness rise sharply and eventually level off.
How does the polymer molecular weight affect its solution viscosity?
The larger the polymer, the more drag and also the more intermolecular attraction, and so the higher the viscosity. So, the viscosity increases with the molecular weight, but not necessarily in a linear way.
Does a higher molecular weight increase solubility?
Within alkanes, molecular size is the primary determinant of their solubility in water, and increasing molecular size results in a decrease in water solubility mainly due to the increased free energy penalty for cavity formation in water.
How does molecular weight affect tensile strength?
A higher molecular weight also means that there is more increased chain entanglement. This bring about an increase in tensile strength and elastic modulus due to the fact that more energy is required to break or loosen the entangled chains.
What factors affect the properties of polymers?
Numerous factors affect various mechanical properties of polymers, in- cluding molecular weight, processing, extent and distribution of crystallinity, composition of polymer, and use temperature.
What can impact the physical properties of a polymer?
The processing conditions which can affect the properties of the polymer include the temperature and pressure used during the polymerization, the solvent in which the polymer is polymerized, the types of monomer units used, the concentration of monomers in the reaction, the reagent which is used to initiate the …
Which of the following methods is not used for determination of molecular weight?
1. Which of the following methods cannot be used to determine the molecular weight of enzymes? Explanation: Biosensors cannot be used to determine molecular weight of enzymes.