The molecular weight of a polymer significantly affects its properties and functionality. Some of the key properties influenced by molecular weight include mechanical strength, thermal stability, viscosity, solubility, and chemical resistance. Here's a brief overview of how molecular weight impacts these properties:1. Mechanical strength: Generally, polymers with higher molecular weight exhibit greater mechanical strength, such as tensile strength and impact resistance. This is because the longer polymer chains can entangle and form stronger intermolecular interactions, leading to better load-bearing capacity.2. Thermal stability: Polymers with higher molecular weight typically have higher melting and glass transition temperatures. This is because the increased chain length and entanglements make it more difficult for the polymer chains to move and rearrange, thus requiring more energy to change their state.3. Viscosity: The viscosity of a polymer solution or melt increases with increasing molecular weight. Longer polymer chains have more entanglements and a larger hydrodynamic volume, which results in higher resistance to flow.4. Solubility: Polymers with lower molecular weight are generally more soluble in solvents than those with higher molecular weight. This is because shorter chains have a larger surface area to volume ratio, allowing for better interaction with the solvent molecules.5. Chemical resistance: Polymers with higher molecular weight often exhibit greater resistance to chemical degradation and environmental stress cracking. Longer chains have more entanglements and a lower number of chain ends, which reduces the likelihood of chain scission and other degradation processes.There are several methods for measuring the molecular weight of polymers, including:1. Gel permeation chromatography GPC or size exclusion chromatography SEC : This technique separates polymer chains based on their hydrodynamic volume in solution. By comparing the elution time of the polymer sample to that of known standards, the molecular weight can be determined.2. Static light scattering SLS : This method measures the intensity of scattered light from a polymer solution and relates it to the molecular weight using the Zimm plot or Debye plot. SLS provides an absolute measurement of molecular weight without the need for calibration standards.3. Dynamic light scattering DLS : DLS measures the fluctuations in scattered light intensity due to the Brownian motion of polymer chains in solution. The diffusion coefficient can be determined, which can then be related to the hydrodynamic radius and molecular weight using the Stokes-Einstein equation.4. Osmometry: Osmotic pressure measurements can be used to determine the number-average molecular weight of a polymer. This method is based on the relationship between osmotic pressure and polymer concentration in a dilute solution.5. Ultracentrifugation: Analytical ultracentrifugation can be used to determine the sedimentation coefficient of a polymer in solution, which can then be related to the molecular weight using the Svedberg equation.Each of these methods has its advantages and limitations, and the choice of method depends on factors such as the polymer type, molecular weight range, and the required accuracy and precision of the measurement.