Rigid, Helical Arm Stars through Living Nickel Polymerization of Carbodiimides

Abstract

Using the core-first growth strategy, we have synthesized a tris-Ni­(II) initiator which bears three initiating sites for the ensuing polymerization of N-1-phenethyl-N′-methyl­carbodiimide. The arms of these star polymers bearing chiral side chains adopt single-handed helical rod-like conformations. The polymerization occurs in a controlled, living fashion, and this multiarm architecture imparts a new set of intriguing properties including their self-assembly into diverse nanostructures when cast from different solvents. These assemblies, characterized by AFM, TEM, and DLS, include the formation of nanofiber networks and twisted superhelical nanostructures. Interestingly, by processing these polymers via electrospraying method, hollow and uniform platelet-like particles were obtained. These solvent-dependent morphologies of microparticles were observed by using SEM. The kinetic studies of polymerizations, inspection of self-aggregation behaviors, and electrosprayed architectures will open up possibilities for a variety of potential biomedical applications.

UV- and Thermo-Controllable Azobenzene-Decorated Polycarbodiimide Molecular Springs

“…The initial SOR for the ( R )- N -methyl- N ′-phenethylcarbodiimide monomer was +48°, and the resulting polymers P-2 and P-3 showed oppositely signed SOR of −113° and −156°, respectively. Thus, it is conclusive that the polymer helicity is governed by the helical backbone . The homopolymer synthesized from ( R )- N -methyl- N ′-phenethyl­carbodiimide monomer does not show any changes in SOR values upon UV-illumination or heating; thus, it is conclusive that changes in SOR values are solely due to dynamic isomerization of azobenzene pendants.…”

“…Thus, it is conclusive that the polymer helicity is governed by the helical backbone. 41 The homopolymer synthesized from (R)-N-methyl-N′-phenethylcarbodiimide monomer does not show any changes in SOR values upon UV-illumination or heating; thus, it is conclusive that changes in SOR values are solely due to dynamic isomerization of azobenzene pendants. We attempted to induce configurational changes in the azobenzene moiety through the irradiation of polymer samples by using UV 365 nm.…”

Cellulose Concurrently Induces Predominantly One-Handed Helicity in Helical Polymers and Controls the Shape of Optically Active Particles Thereof

“…We envision that nonspherical particles derived from chiral polymers may provide new materials with unprecedented properties and potential applications in chiral resolution, drug release, chiral sensors, and photonic devices. Most recently, Novak et al reported chiral helical polymer-constructed platelet-like particles fabricated by electrospinning . In the present contribution, we created a novel strategy for preparing nonspherical chiral helical polymer particles, i.e.…”

Developments in synthesis, characterization, and self‐assembly of polycarbodiimide systems

“…To achieve multi‐arm star polymers, both core‐first strategy and arm‐first method can be employed. In this regard, we attempted arm‐first method by synthesizing nitrile end‐functionalized PPMC using Initiator‐4 . Unfortunately, the trimerization reaction of the nitrile group in the presence of neat triflic acid (CF 3 SO 3 H) was not successful.…”

“…Again, taking advantage of the “living” nickel(II)‐mediated polymerization of carbodiimides, Siriwardane et al synthesized three‐arm star polymers with chiral, rigid‐rod PPMC arms extending radially from a central core . These polymers were found to adopt unique nanoscale aggregates when compared to linear PPMC analogues.…”