Chemoselective Polymerizations from Mixtures of Epoxide, Lactone, Anhydride, and Carbon Dioxide

Controlling polymer composition starting
from mixtures of monomers
is an important, but rarely achieved, target. Here a single switchable
catalyst for both ring-opening polymerization (ROP) of lactones and
ring-opening copolymerization (ROCOP) of epoxides, anhydrides, and
CO2 is investigated, using both experimental and theoretical
methods. Different combinations of four model monomersε-caprolactone,
cyclohexene oxide, phthalic anhydride, and carbon dioxideare
investigated using a single dizinc catalyst. The catalyst switches
between the distinct polymerization cycles and shows high monomer
selectivity, resulting in block sequence control and predictable compositions
(esters and carbonates) in the polymer chain. The understanding gained
of the orthogonal reactivity of monomers, specifically controlled
by the nature of the metal-chain end group, opens the way to engineer
polymer block sequences.