Chemical recycling to monomers (CRM) offers a promising
closed-loop
approach to transition from current linear plastic economy toward
a more sustainable circular paradigm. Typically, this approach has
focused on modulating the ceiling temperature (T
c) of monomers. Despite considerable advancements, polymers
with low T
c often face challenges such
as inadequate thermal stability, exemplified by poly(γ-butyrolactone)
(PGBL) with a decomposition temperature of ∼200 °C. In
contrast, floor temperature (T
f)-regulated
polymers, particularly those synthesized via the ring-opening polymerization
(ROP) of macrolactones, inherently exhibit enhanced thermodynamic
stability as the temperature increases. However, the development of
those T
f regulated chemically recyclable
polymers remains relatively underexplored. In this context, by judicious
design and efficient synthesis of a biobased macrocyclic diester monomer
(HOD), we developed a type of T
f -regulated
closed-loop chemically recyclable poly(ketal-ester) (PHOD). First,
the entropy-driven ROP of HOD generated high-molar mass PHOD with
exceptional thermal stability with a T
d,5% reaching up to 353 °C. Notably, it maintains a high T
d,5% of 345 °C even without removing the
polymerization catalyst. This contrasts markedly with PGBL, which
spontaneously depolymerizes back to the monomer above its T
c in the presence of catalyst. Second, PHOD
displays outstanding closed-loop chemical recyclability at room temperature
within just 1 min with
t
BuOK. Finally,
copolymerization of pentadecanolide (PDL) with HOD generated high-performance
copolymers (PHOD-co-PPDL) with tunable mechanical
properties and chemical recyclability of both components.