posted on 2018-04-06, 18:21authored byNolan
M. Gallagher, Aleksandr V. Zhukhovitskiy, Hung V.-T. Nguyen, Jeremiah A. Johnson
Polyzwitterions have found extensive
applications in biological
and materials sciences. Despite this success, most polyzwitterions
have nondegradable polyolefin backbones with pendant zwitterionic
groups. Transcension of this structural paradigm via the formation
of main-chain zwitterionic supramolecular polymers could lead to readily
processable, as well as self-healing and/or degradable, polyzwitterions.
Herein, we report the synthesis and characterization of poly(azolium
amidinate)s (PAzAms), which are a new class of supramolecular main-chain
polyzwitterions assembled via the formation of N-heterocyclic
carbene–carbodiimide (NHC–CDI) adducts. These polymers
exhibit a wide range of tunable dynamic properties due to the highly
structure-sensitive equilibrium between the NHC–CDI adduct
and its constituent NHCs and CDIs: e.g., PAzAms derived from N-aryl-N′-alkyl CDIs are dynamic
at lower temperatures than those derived from N,N′-diaryl CDIs. We develop a versatile synthetic
platform that provides access to PAzAms with control over the main-chain
charge sequence and molecular weight. In addition, block copolymers
incorporating PAzAm and poly(ethylene glycol) (PEG) blocks are water
soluble (>30 mg mL–1) and self-assemble in aqueous
environments. This work defines structure–property relationships
for a new class of degradable main-chain zwitterionic supramolecular
polymers, setting the stage for the development of these polymers
in a range of applications.