One-Pot Synthesis, Circularly Polarized Luminescence, and Controlled Self-Assembly of Janus-Type Miktoarm Star Copolymers

With the aim of broadening the scope of Janus-type polymers with new functionalities, Janus-type miktoarm star copolymers comprising helical poly(phenyl isocyanide) (PPI) and a vinyl polymer were designed and synthesized via a combination of Pd(II)-initiated isocyanide polymerization and atom transfer radical polymerization (ATRP). A functional β-cyclodextrin bearing 7 Pd(II) complexes at one side and 14 bromine groups at the other side ((Pd(II))7-CD-(Br)14) was prepared and used as an initiator for the one-pot polymerization of phenyl isocyanide and the ATRP of vinyl monomers in a living and controlled manner. A variety of Janus-type copolymers with different structures and tunable compositions were facilely obtained by using this method. Thus, Janus-type copolymers composed of helical PPIs and tetraphenylethylene-modified vinyl polymers exhibited a significant circularly polarized luminescence performance in both soluble and aggregated states. Meanwhile, Janus-type copolymers containing PPIs and hydrophilic vinyl polymers presented amphiphilicity and self-assembled into diverse morphologies.

Alkyne-Palladium(II)-Catalyzed Living Polymerization of Isocyanides: An Exploration of Diverse Structures and Functions

Inspired by the perfect helical structures and the resulting exquisite functions of biomacromolecules, helical polymers have attracted increasing attention in recent years. Polyisocyanide is well known for its distinctive rodlike helical structure and various applications in chiral recognition, enantiomer separation, circularly polarized luminescence, liquid crystallization, and other fields. Although various methods and catalysts for isocyanide polymerization have been reported, the precise synthesis of helical polyisocyanides with controlled molecular weight, low dispersity, and high tacticity remains a formidable challenge. Owing to a limited synthesis strategy, the controlled synthesis of topological polyisocyanides has barely been realized. This Accounts highlights our recent endeavors to explore novel catalysts for the living polymerization of isocyanides. Fortunately, we discovered that alkyne-Pd(II) catalysts could initiate the living polymerization of isocyanides, resulting in helical polyisocyanides with controlled structures, high tacticity, and tunable compositions. These catalysts are applicable to various isocyanide monomers, including alkyl isocyanides, aryl isocyanides, and diisocyanobenzene derivatives. Incorporating chiral bidentate phosphine ligands onto alkyne-Pd(II) complexes formed chiral Pd(II) catalysts, which promoted the asymmetric living polymerization of achiral isocyanide, yielding single left- and right-handed helices with highly optical activities.Using alkyne-Pd(II) catalysts, various topological polyisocyanides have been facilely prepared, including hybrid block copolymers, bottlebrush polymers, core cross-linked star polymers, and organic/inorganic nanoparticles. For instance, various hybrid block polyisocyanides were easily produced by coupling alkyne-Pd(II)-catalyzed living isocyanide polymerization with controlled radical polymerization and ring-opening polymerization (ROP). Combining the ring-opening metathesis polymerization (ROMP) of norbornene with Pd(II)-catalyzed isocyanide polymerization, bottlebrush polyisocyanides and core cross-linked star polymers were easily prepared. Pd(II)-catalyzed living polymerization of poly(lactic acid)s with isocyanide termini resulted in densely grafted bottlebrush polyisocyanides with closely packed side chains. Moreover, the surface-initiated living polymerization of isocyanides produced a family of polyisocyanide-grafted organic/inorganic hybrid nanoparticles using nanoparticles with alkyne-Pd(II) catalysts anchored on the surfaces. Surprisingly, the nanoparticles and star polymers with helical polyisocyanide arms performed exceptionally well in terms of chiral recognition and resolution. Incorporated organocatalysts such as proline and prolinol units onto the pendants of optically active helical polyisocyanides, a family of polymer-based chiral organocatalysts, were generated, which showed significantly improved stereoselectivity for the asymmetric Aldol reaction and Michael addition and can be easily recycled.Using a chiral alkyne-Pd(II) catalyst, single-handed helical polyisocyanides bearing naphthalene and pyrene probes were produced from achiral isocyanide monomers. These polymers showed excellent self-sorting properties as revealed using a fluorescence resonance energy transfer (FRET) investigation and were self-assembled into two-dimensional (2D) smectic nanostructures driven by both helicity and chain length. Incorporating helical poly(phenyl isocyanide) (PPI) onto semiconducting poly(3-hexylthiophene) (P3HT) induced the asymmetric assembly of the resulting P3HT-b-PPI copolymers into single-handed cylindrical micelles with controlled dimensions and tunable photoluminescence.

Chiral helical substituted polyacetylene grafted on hollow polymer particles: preparation and enantioselective adsorption towards cinchona alkaloids

Hollow polymer particles tethering chiral helical polymer chains and functional carboxyl groups were prepared and applied in enantioselective adsorption.