Functional Isocyanide-Based Polymers

Abstract

Conspectus Research interest in the isocyanide-based reaction can be traced back to 1921 when the Passerini reaction was first reported. However, most of these research efforts did not lead to important progress in the synthesis of isocyanide-based polymers (IBPs). The major challenge resides in the lack of highly efficient polymerization methods, which limits large-scale preparation and applications. Modern organic chemistry provides efficient access to develop functional IBPs on the basis of isocyanide chemistry. However, it is still challenging to prepare the IBPs with small molecular isocyanide reaction. Our investigations into catalyst exploration and polymerization methodology have prompted the synthesis of a series of IBPs. Two classes of isocyanide monomers can be used for the construction of IBPs. The first class includes monomers with a single isocyanide. Novel catalysts for the synthetic chemistry of isocyanide allow the introduction of functional pendants into the linear polymer chains. This molecular functionalization endows the polymers with an array of new functional properties. For example, the incorporation of a chromophore on the polymeric side chain provides novel functional properties, such as aggregation-induced emission and optical activity. Diisocyanide monomers can be also utilized for the construction of heterocyclic, spiro-heterocyclic, and bispiro-heterocyclic polymers in the polymeric backbones. A new concept of “multi-component spiropolymerization” has been developed for the preparation of spiropolymers using the catalysis-free one-pot reaction. Proper structural design allows for the preparation of a heterocyclic polymeric chain with natural bioactivity and biological compatibility, generating new IBPs with biofunctionalities. In this Account, we discuss progress mainly made in our lab and related fields for the design of isocyanide monomers, exploration of new catalysts, and optimization of reaction conditions. The subsequent section discusses the characteristic properties and applications of selected examples of these functional polymers, mainly focusing on their optical applications. We have investigated the UV-sensitive IBPs that could potentially be used for lithography applications. One-pot highly efficient polymerization of diisocyanides and CO2 under mild conditions can provide a new method for realizing the reuse of CO2 and reducing the greenhouse effect. Through a combination of structural modifications, IBPs bearing dimethylbenzene moieties exhibit characteristics of black materials that can be potentially utilized as pyroelectric sensors, thermal detectors, and optical instruments. Most recently, our group synthesized a spiro-heterocyclic IBP with clusterization-triggered emission properties that can be used to discriminate cancer cells from normal cells and provides a new method for the treatment of cancer. The studies reviewed in this Account suggest that polymerization with isocyanide chemistry can be implemented in diverse functional macromolecules and materials.

Multicomponent Polymerization of Alkynes, Isocyanides, and Isocyanates toward Heterocyclic Polymers

“…Although a great deal of research on the isocyanide-based MCRs, − which play crucial roles in organic synthesis, drug discovery, and materials science, has been conducted, − there have been few empirical investigations into isocyanide-based MCPs. ,− Among the reported isocyanide-based reactions, we were intrigued by a catalyst-free cyclization of isocyanides, isocyanates, and alkynes, in which maleimide derivatives can be efficiently produced in high yields . Such a reaction holds great potential to be developed into a MCP, which could furnish functional heterocyclic polymers that are potentially applicable in gene delivery, controlled drug release, optoelectronic materials, coatings and adhesives, and so forth. − Moreover, the monomers for the polymerization are easily accessible with merely a rational design of diisocyanides.…”

In Situ Generation of Heterocyclic Polymers by Triple‐Bond Based Polymerizations

“…Dong's group has also made great contributions for the in-situ construction of five-membered heterocyclic polymers based on isonitriles. [37][38][39][40][41][42][43] For example, they reported a catalystfree cyclopolymerization of diisocyanide, dialkylacetylene dicarboxylates and dialdehyde in 2019 (Scheme 2C). [42] The reaction in situ generated poly(amine-furan-arylene)s with high molecular weights (M w up to 76 400 g mol −1 ) and good thermal stability under mild conditions.…”

Multicomponent Spiropolymerization of Diisocyanides, Diethyl Acetylenedicarboxylate, and Halogenated Quinones

“…Recently, our group developed MCSPs for preparing functional spiropolymers using alkynes, diisocyanides, and the third monomer containing the C=O group via catalyst-free one-pot conditions. [39,40] In addition, functional heterocyclic polymers have been obtained from various third monomers containing the C=O group, such as polyfurans, polyiminofurans, and poly(iminofuranarylene)s. [41][42][43][44] Based on previous work, quinones containing two C=O groups attracted our interest. The compounds are often used for the preparation of functional polymers, such as electrodes, hydrogels, and fluorescent dyes.…”