Progress in Isocyanide‐Based Step‐Growth Polymerization

Abstract

Isocyanide is an important class of active synthon with a special electronic structure and abundant chemical properties, which can participate in various organic reactions and has a wide range of applications in the efficient synthesis of pharmaceutical molecules, heterocyclic compounds, and natural products, etc. With the development of chemical science, isocyanide-based reactions have been gradually applied from the synthesis of low mass molecules to functional polymers. This review focuses on the recent progress in isocyanide-based step-growth polymerization, as well as the properties and applications of the resultant functional polymers. These polymerizations are divided into six main parts including Passerini polymerization, Ugi polymerization, multicomponent polymerization (MCP) of isocyanide and dialkylacetylenedicarboxylates (DAADs), MCP of isocyanide and green monomer, MCP of isocyanide and industrial waste, as well as the polymerization based on isocyanoacetate. The existing challenges and the promising opportunities are concisely discussed.

Efficient Conversion of Inert Nitriles to Multifunctional Poly(5-amino-1,2,3-triazole)s via Regioselective Click Polymerization with Azide Monomers under Ambient Conditions

“…After stone, ceramic, concrete, bronze, iron, aluminum, and steel, synthetic polymers are the most significant development for human cognition and application of matter and materials, which play important roles in anthropic production and life . The establishment of new polymerizations is an inevitable tendency in synthetic polymer chemistry and materials science, especially with the advantages of simple operation, mild conditions, high efficiency, excellent selectivity, low cost, environmental benefits, and so on. − Recently, polymerizations based on triple-bond building blocks, such as Sonogashira coupling polymerization, , Glaser coupling polymerization, , polycyclotrimerization, , C–H activation polymerization, − click polymerization, − and multicomponent polymerization, − have attracted broad attention because of their abundant reaction types and high reactivity. Moreover, the polymers generated by these powerful polymerizations contain unique unsaturated conjugated units, making them widely applicable in chemical sensor, information encryption, optoelectronic and biologic fields, and so on. − …”

Catalyst-free multicomponent polymerization of aldehydes, amines and trimethylsilyl cyanide toward poly(α-aminonitrile)s

“…Recently, multicomponent polymerizations (MCPs) have become a popular polymer synthesizing tool, which has gained much attention in designing new polymeric structures and regulating material properties, [12][13][14] including isocyanidebased MCPs, [15][16][17][18][19][20][21] alkyne-based MCPs, [22][23][24][25][26] elemental sulfurbased MCPs, [27][28][29] green monomer-based MCPs 30 and so forth. 31 Compared with traditional polymerizations, MCPs could provide polymers with well-defined structures, ordered sequences of monomer units, and multifunctionalities, featuring advantages of high atom economy, step effectiveness, environmental benefits, simple and inexpensive reactants, operational simplicity, and synthetic efficiency.…”

Chemical Recycling of Step-Growth Polymers Guided by Le Chatelier’s Principle

“…To address the end-of-life issue of SGPs, by depolymerizing them into either their starting feedstocks or derivatives, followed by repolymerization or repurposing into virgin-quality or value-added polymersa process termed chemical recyclingpresents a promising solution. − Most conventional SGPs such as polyesters, polyamides, and polycarbonates are synthesized by condensation reactionswhere difunctional or multifunctional monomers link togetherlosing small molecules as byproducts. − Condensation reactions are intrinsically reversible and exist in dynamic equilibrium with their hydrolysis reactions, and an exhaustive condensation requires timely removal of byproducts from the reaction system. − The presence of such byproducts detrimentally impacts the polymerization degree of resulting condensation polymers. Other types of conventional SGPs primarily including polyurethanes and polyureas are formed by addition reactions that simply link monomers without the cogeneration of byproducts . Recently, researchers found that these two addition polymers (i.e., polyurethanes and polyureas) exhibit dynamic behavior upon thermal treatment typically above 180 °C, undergoing dissociation into their constituent reactantsnamely isocyanates and hydroxyls (for polyurethanes) or amines (for polyureas), respectively. − These indicate that regardless of the synthetic route (i.e., condensation and addition), most resulting SGPs inherently possess a “dynamic” characteristic; one is the equilibrium between condensation and hydrolysis reactions, and the other refers to the equilibrium between addition reactions and thermal dissociation.…”

“…Other types of conventional SGPs primarily including polyurethanes and polyureas are formed by addition reactions that simply link monomers without the cogeneration of byproducts. 37 Recently, researchers found that these two addition polymers (i.e., polyurethanes and polyureas) exhibit dynamic behavior upon thermal treatment typically above 180 °C, undergoing dissociation into their constituent reactants� namely isocyanates and hydroxyls (for polyurethanes) or amines (for polyureas), respectively. 38−40 These indicate that regardless of the synthetic route (i.e., condensation and addition), most resulting SGPs inherently possess a "dynamic" characteristic; one is the equilibrium between condensation and hydrolysis reactions, and the other refers to the equilibrium between addition reactions and thermal dissociation.…”