Light Scattering Studies of Poly(methyl Methacrylate)/(Poly(ethyl Acrylate)/Poly(butyl Acrylate)) Terpolymer

摘要

The classical Bushuk-Benoit light scattering theory for solutions of copolymers is extended to solutions of (quasi)terpolymers which may be polydisperse in chain composition as well as in molecular weight. A method for determining the weight-average molecular weight of a (quasi)terpolymer with only three solvents is described. The scheme was tested by using a poly(methyl methacrylate)(poly(ethyl acrylate)/poly(butyl acrylate)terpolymer (PMMA/PEA/PBA) and five solvents: methyl ethyl ketone (MEK), dioxane (DIO), ethyl acetate (EA), cyclohexanone (CYC), and m-dichlorobenzene (MDCB), covering a very broad refreactive index increment range. The apparent molecular wright varies from 1,370,000 in ethyl acetate to 1.80 x 10 to the 6th power in cyclohexanone. One important factor in achieving a more precise molecular weight determination is the spread of the refractive index increment from -0.0391 in m-dichlorobenzene to 0.122 in ethyl acetate. The (true) molecular weight of the (quasi)terpolymer was determined to be approx. 1,200,000. Intensity time correlation functions of PMMA/(PEA/PBA) (quasi)terpolymer, provided that the properties of (PEA/PBA) are so similiar as to have an average refractive index covering both monomer types.