Infrared Determination of Composition of Ethylene-Propylene Copolymers

Abstract

Abstract Carbon-14 labeled ethylene and propylene were used to synthesize a series of copolymers of known composition to serve as standards for copolymer analyses. Polymers with broad and narrow compositional distributions and differing sequence distributions were produced by varying the catalyst system. Solution and combustion counting techniques were used to determine sample composition and then infrared calibration curves were determined on pressed polymer films utilizing several different infrared peaks. 1. Within the ranges systematically varied neither compositional nor sequence distributions affect the peak ratios studied. 2. No isotope effects exist in the polymerizations. 3. NMR analysis yields the same results as 14C analysis. 4. Use of the 1378 cm−1 methyl band as calibrated with atactic polypropylene yields agreement with the 14C data if the average of polypropylene and copolymer results is used. 5. We amend the results previously published by our laboratory.