8 methods to determine the molecular weight of polymers

related topics . There are many methods for the experimental method of molecular weight determination and the molecular weight of the strong weapon metric high
molecule
, the most common being the following 8 methods 1, end-based analysis method. The amount of
molecule
is derived by measuring the specific end-base content by chemical analysis, provided that the polymer structure is fully understood and it can also be used for the determination of the number of branch chains. The molecular weight of this method is not generally too large.2, the boiling point rises and the freezing point decreases. This is a classical physical and chemical method for determining the amount of
molecules
by using the dependence of the thin solution. After the non-volatile solution is added to the solvent, the vapor pressure of the solution decreases, resulting in the solution's boiling point being higher than that of the pure solvent and the solution's freezing point being lower than that of the solvent. This method has not been used, the temperature difference measurement accuracy is very high.3, membrane permeation pressure. It should also be a physical and chemical method to measure permeable pressure by semi-permeable membrane. It seems to be a lot of trouble, and it's not used.4, gas phase osmosis (VPO). The amount of pure molecules was measured using a pure solvent different from the saturated vapor pressure of the solution
the
solution. The measured is the average molecular weight. It hasn't been used.5, light scattering/small angle laser light scattering (LALLS). These two methods are only instruments, data processing and the use of light sources and other aspects of the difference, the principle is similar. This method is more commonly used, and the instrument has now developed to a certain level, is the most effective way
testing
of high molecular weight and absolute molecular weight.6, overspeed centrifugal subside. It is complex and was first used
the
proteins and molecules. is a relative approach. It hasn't been used.7, Gel
Chromatography
(GPC). It is commonly used to measure molecular weights based on how long molecules of different sizes stay in the medium. is a relative method that needs to be combined with other methods.8, viscosity method. Too common, using glass
viscosity meter
(Ukrainian viscosity meter, O viscosity meter) to increase viscosity, and then external tweeting viscosity, according to the Mark-Houwink equation to calculate the molecular weight, is the most economical method, and re-degree is very good. Water-soluble polymers generally measure molecular weight in this way and are a relative method
.