MayoLewis

MayoLewis, also known as the Mayo–Lewis equation, is a relation in polymer chemistry that describes the instantaneous composition of a copolymer formed from two monomers during free-radical copolymerization. The equation connects the copolymer composition to the monomer feed composition and the monomer reactivity ratios r1 and r2, which quantify how each monomer adds to a growing chain ending in either monomer unit. In this framework, F1 denotes the mole fraction of monomer M1 in the polymer, and f1 and f2 denote the mole fractions of M1 and M2 in the monomer feed (with f1 + f2 = 1). The Mayo–Lewis relation provides F1 as a function of f1, f2, r1, and r2. The reactivity ratios are defined as r1 = k11/k12 and r2 = k22/k21, where kij are rate constants for the various addition steps.

Named after the researchers Mayo and Lewis, who introduced it in the mid-20th century, the equation has become a standard tool in polymer science. It is used to interpret experimental copolymer compositions and to estimate reactivity ratios from data, via methods such as Fineman–Ross or Kelen–Tüdő plots.

Limitations include the assumption of constant reactivity ratios, low conversion to minimize compositional drift, and applicability to two-monomer radical polymerizations; deviations from ideal behavior or other polymerization mechanisms can reduce accuracy.

Applications include designing copolymers with targeted compositions and properties, studying monomer compatibility, and understanding tendencies toward random, alternating, or blocky sequences in copolymers.