Study On Polymers Molecular Weight Measuring Technique Based On Static Light Scattering

The molecular weight being the most basic and important parameter has a great impact on processing,physical properties and application of the polymer material.Static light scattering is the absolute method of measuring the weight average molecular weight,and has been widely used because of its features which are large measurement range,high accuracy,good repeatability and contact-free.So the paper researched on molecular weight measuring technology of polymer based on static light scattering,the main research contents include:Firstly,the molecular weight measured by static light scattering theory was analyzed:based on the principle scattering of light by ideal gas molecules,dilute solution of small particles and large particles,the expression of static light scattering was deduced.The dependence of different polarization directions of the incident light on the scattered light intensity is analyzed.In various scattering angles,different various sizes of particle scattering function of homogeneous spheres and random coils instituted to the approximate scattering function is studied.Secondly,the limitations of different methods of Debye,Zimm and Berry extrapolating formalisms constructing Debye graphs were analyzed.the relative error in molecule weight and root mean square radius depending on three extrapolation of Debye,Zimm and Berry methods for constructing the Debye plot of various size of the random coils and homogeneous spheres were studied.The effect the angular interval used for the extrapolation and robustness of the different different extrapolating methods toward errors in the measured light scattering intensity at low angle were investigated.Thirdly,according to the principle of beam refraction,the relationship between the beam deviation and the solution refractive index increment was deduced,and the f-2f optical path was designed.The differential refractometer section of static light scattering device was designed,and the calibration method of device was proposed.Fourthly,static light scattering instrument device was designed,optical components,temperature measurement,temperature control device and scattered light intensity detecting device were designed and installed.The molecular weight and root mean square radius of polystyrene were measured by Debye,Zimm and Berry extrapolating formalisms,and the results were compared with those of the random coil fit method.