Lithium achieves sequence selective ring-opening terpolymerisation (ROTERP) of ternary monomer mixtures

Heteroatom-containing degradable polymers have strong potential as sustainable replacements for petrochemically derived materials. However, to accelerate and broaden their uptake greater structural diversity and new synthetic methodologies are required. Here we report a sequence selective ring-opening terpolymerisation (ROTERP), in which three monomers (A, B, C) are selectively enchained into an (ABA ' C)(n) sequence by a simple lithium catalyst. Degradable poly(ester-alt-ester-alt-trithiocarbonate)s are obtained in a M-n range from 2.35 to 111.20 kDa which are not easily accessible via other polymerisation methodologies. The choice of alkali metal is key to achieve high activity and to control the terpolymer sequence. ROTERP is mechanistically compatible with ring-opening polymerisation (ROP) allowing switchable catalysis for blockpolymer synthesis. The ROTERP demonstrated in this study could be the first example of an entirely new family of sequence selective terpolymerisations.

Automated summary

Heteroatom-containing degradable polymers have strong potential as sustainable replacements for petrochemically derived materials. To accelerate and broaden their uptake, greater structural diversity and new synthetic methodologies are required. This study reports a sequence selective ring-opening terpolymerisation (ROTERP), which selectively enchains three monomers into a specific sequence using a simple lithium catalyst. The obtained degradable poly(ester-alt-ester-alt-trithiocarbonate)s have a molecular weight range from 2.35 to 111.20 kDa, which are not easily accessible via other polymerisation methodologies. The ROTERP demonstrated in this study could be the first example of an entirely new family of sequence selective terpolymerisations.