A Polymer with “Locked” Degradability: Superior Backbone Stability and Accessible Degradability Enabled by Mechanophore Installation

Though numerous applications require
degradable polymers, there
are surprisingly few polymer systems that combine superior stability
and controllable degradability. Particularly, the degradability of
a conventional degradable polymer is typically enabled by cleavable
groups on the backbone, which can be attacked by stimuli in ambient
conditions, causing undesirable material deterioration. Here we report
a general strategy to overcome this issue: “locking”
the degradability during handling and use of the polymers and “unlocking”
it when degradation is needed. This strategy is demonstrated with
a cyclobutane-fused lactone (CBL) polymer. The cyclobutane keeps polymer
backbone intact under conditions that hydrolyze the lactone and allows
the ester group to be recovered when undesirable hydrolysis occurs.
When backbone degradation is needed, the degradability can be unlocked
by mechanochemical activation that converts the polyCBL into a linear
polyester. The rare combination of two intrinsically conflicting properties,
i.e., backbone stability and accessible degradability, can make this
polymer a potential option for new sustainable materials.