Poly(ester-alt-ethers) can combine beneficial ether linkage flexibility and polarity, with ester linkage hydrolysability furnishing fully degradable polymers. Despite their promising properties, this class of polymers remains underexplored, in part due to difficulties in polymer synthesis. Here, a catalyzed copolymerization using commercially available
monomers, butylene oxide (BO)/oxetane (OX), tetrahydrofuran (THF) and phthalic anhydride (PA), accesses a series of
well defined, poly(ester-alt-ethers). A Zr(IV) catalyst is reported that yields polymer repeat units comprising a ring-opened
PA (A) followed by two ring-opened cyclic ethers (B/C) (-ABB- or -ABC-). It operates with high polymerization control,
good rate and successfully enchains epoxides, oxetane and/or tetrahydrofurans (THF) – providing a straightforward means
to moderate the distance between ester linkages. Kinetic analyses of PA/BO copolymerization, with/without THF, reveals
an overall second-order rate law: first order in both catalyst and butylene oxide concentrations, but zero-order in phthalic
anhydride and, where it is present, zero-order in THF. The poly(ester-alt-ethers) have lower glass transition temperatures
(-16
faster ester hydrolysis rates compared with analogous AB polymers. The Zr(IV) catalyst furnishes poly(ester-alt-ethers) from
a range of commercially available epoxides and anhydride; it presents a straightforward method to moderate degradable
polymers’ properties.
