Fractionation of a copolymer of methyl methacrylate and methacrylic acid and the properties of the fractions

Abstract

Poly-(methyl methacrylate) (PMMA) is one of the most widely used polymeric products, but in some cases it is desirable to modify a number of its properties. This is achieved most simply by copolymerizing methyl methacrylate with appropriate unsaturated compounds. In order to increase the surface hardness of articles and raise the glass temperature, a polar unsaturated compound is used, as a rule as the second component. A marked influence on many of the properties of the copolymer can be exerted by introducing metal salts into the composition of its macromolecule [1]. Usually, when unsaturated metal salts are added to the reaction mixture, the kinetics of the copolymerization change fundamentally and the final product possesses a series of new properties. One of the main reasons for the changes in the properties of bulk polymers is a change in the physical and chemical characteristics of the macromoleculles Consequently, an investigation of the properties of the macromolecules of copolymers of methyl methacrylate (MMA) and methacrylic acid (MAA) is extremely urgent. An analysis of the main physical magnitudes characterizing the macromolecules in solution for copolymers of various compositions permits valuable information to be obtained on the cause of change of these magnitudes with a change in the chemical composition of the copolymer. In the present work, we have subjected to fractionation a copolymer containing 92·6% of MMA and 7·4% of MAA (weight concentrations) with a very small amount of added lithium salt of MAA. The lithium salt was added with the function of introducing “labelled atoms”. The fractions obtained were subjected to investigation by the methods of light dispersion and viscosimetry.