Copolymer Compositional Drift MeasurementFebruary 2009 Polymers require a broad array of physical, thermal and chemical properties. There is a need to be able to tailor polymer materials synthesis to specific property sets. Commercial homopolymers are limited in their ability to be adjusted for simultaneous requirements, such as elasticity, impact strength, thermal transitions, and environmental resistance. This can be addressed to an extent with polymer blends, but compatibility and possible poor qualities of any of the blend components affect the finished blend product. Copolymers provide a continuum of adjustment in the characteristics of the individual comonomer constituents, and are a flexible way to tailor product finish properties. An aspect of copolymer synthesis that must be managed is Composition Drift: a variation of the relative amounts of comonomer species incorporated into the growing polymer chains during polymerization. Small variations in the concentration of comonomers in the reaction environment or any difference in monomer reactivities will generate composition drift during synthesis. The synthesis process must incorporate controls to either reduce composition drift, or to tailor it to a profile that yields desired product finish properties. This Application note describes a rapid and simple way to characterize composition drift in polymers. Such drift is most commonly measured against the molecular weight distribution, as determined by Gel Permeation Chromatography of the copolymer. Click here to view this entire PDF
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