Department of Chemistry, William Mong Institute of Nano Science and Technology, Bioengineering Graduate Program, The Hong Kong University of Science & Technology (HKUST), Clear Water Bay, Kowloon, Hong Kong, China, and Department of Polymer Science and Engineering, Key Laboratory of Macromolecular Synthesis and Functionalization of the Ministry of Education, Institute of Biomedical Macromolecules, Zhejiang University, Hangzhou 310027, China

Acetylenic polymers: syntheses, structures, and functions.

Water is truly ubiquitous. Approximately 80% of the earth’s surface is covered by water, although only 1% of this is drinkable water. Water is the solvent of life and makes up about 60% of the mass of the human body. The majority of synthetic organic chemistry carried out in research laboratories or industrial processes utilizes organic solvents, however. Organic solvents have a number of attractive features: they will dissolve a wide range of organic compounds, they come with a variety of properties, and they are often volatile and easily removed. Unfortunately, organic solvents are often toxic, flammable, and nonrenewable and have low heat capacities. In contrast, water is nontoxic and nonflammable, has a high heat capacity, and is relatively inexpensive. Of course water has some significant drawbacks as a solvent: it is a poor solvent for most organic molecules, and it is highly reactive with many classes of reagents. Because of these drawbacks, water is rarely used as a primary solvent in synthetic organic chemistry, although there is a growing body of work related to organic chemistry in water.1-3

Hydrophilic Ligands and Their Application in Aqueous-Phase Metal-Catalyzed Reactions

Polymerization reactions of phenylacetylene derivatives are promoted by rhodium complexes within the discrete space of apo-ferritin in aqueous media. The catalytic reaction provides polymers with restricted molecular weight and a narrow molecular weight distribution. These results suggest that protein nanocages have potential for use as various reaction spaces through immobilization of metal catalysts on the interior surfaces of the protein cages.

Polymerization of phenylacetylene by rhodium complexes within a discrete space of apo-ferritin.

For many years, considerable research efforts have been dedicated to π-conjugated polymers because of their extraordinary electronic, optical, and structural properties. The employed transition-metal-based initiating systems comprise not only simple transition-metal salts but also rather sophisticated mixtures of two, three, or four compounds and even highly defined single-component systems such as transition-metal alkylidene complexes. Extensive fine-tuning of the electronic and steric properties of initiator–monomer systems eventually allowed the tailor-made synthesis of conjugated materials via living polymerization techniques. This article focuses on recent developments in the field of the living polymerization of substituted acetylene derivatives. Ill-defined group 5 and 6 transition metal halide-based initiators, well-defined transition-metal alkylidene complexes, and rhodium(I)-based systems that induce the living polymerization of numerous substituted acetylenes are reviewed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5723–5747, 2005

Living polymerization of substituted acetylenes

In the last fifteen years, a large variety of specialty polymers of diverse chemical structure and functionality have been synthesized with the rhodium-based catalysts The high tolerance to the reaction medium and functional groups of monomers, as well as ability to control various structure features of the polymer formed are typical properties of these catalysts In addition, some rhodium catalysts can be anchored to inorganic or organic supports or dissolved in ionic liquids to form heterophase polymerization systems, which opens the way to pure, well-defined polymers free of the catalyst residues, as well as to recycling rhodium catalysts This review provides a survey on the polymerization reactions induced with rhodium-based catalysts, in which one or more structure attributes of the polymer formed are subject to control The structure attributes considered are (i) sequential arrangement of monomeric units along polymer chains; (ii) head-tail isomerism of polymer molecules; (iii) configurational structure of polymer molecules; (iv) conformation of polymer molecules; and (v) molecular weight and molecular-weight distribution of the polymer formed A review with 188 references

Controlled and Living Polymerizations Induced with Rhodium Catalysts. A Review

It was proved that a Rh-based ternary catalyst composed of [(nbd)RhCl] 2 ) (nbd: bicyclo[2.2.]hepta-2.5-diene), (triphenylvinyl)lithium, and triphenylphosphine induces living polymerization of phenylacetylene. [(nbd)RhCl] 2 was effective as the main catalyst, whereas neither [(cod)RhCl] 2 (cod: 1.5-cyclooctadiene) nor [(coe),RhCl] 2 (coe: cyclooctene) induced living polymerization. The anionie ligands such as chlorine, methoxy, and acetoxy groups in the Rh complex hardly affected the living polymerization. When vinyllithium as second catalyst component possessed a bulky substituent such as phenyl or t-butyl group on its α-carbon, stable vinylrhodium species were generated, which led to living polymerization. At least one substitnent was necessary on the β-carbon of the vinyllithium for the living polymerization. Tris(4-substituted phenylphosphines worked well as third components among various phosphorus ligands. The polymerization was decelerated as the baslcity of the phosphine ligand increased.

Living polymerization of phenylacetylene by rhodium‐based ternary catalysts, (diene)Rh(I) complex/vinyllithium/phosphorus ligand. Effects of catalyst components

Remarkable cocatalytic effect of organometallics and rate control by triphenylphosphine in the Rh-catalyzed polymerization of phenylacetylene

The synthesis of a star polymer with poly(phenylacetylene) arms was examined. 1,4-Diethynylbenzene, which has a similar structure to the monomer, was added as linking agent to the living polymerization system of phenylacetylene by [(nbd)RhCl]2/Ph2CC(Ph)Li/Ph3P ternary catalyst. A star polymer was selectively formed, and the linear polymer was virtually completely consumed. The Mn and arm number of a typical star polymer were 145 000 and 25, respectively. Since the arm number of the star polymer increased with increasing concentration of the linking agent and temperature of the linking reaction and with decreasing DPn of the linear polymer, the arm number could be controlled by these factors. Further, star block copolymers composed of blocks of phenylacetylene and (4-methylphenyl)acetylene were prepared.

Synthesis of a conjugated star polymer and star block copolymers based on the living polymerization of phenylacetylenes with a rh catalyst

Synthesis of poly(phenylacetylene)-block-poly(β-propiolactone) by use of Rh-catalyzed living polymerization of phenylacetylene

A novel, water-soluble Rh complex, (nbd)Rh[PPh2(m-NaOSO2C6H4)] [C(Ph)CPh2] (1) was synthesized by the reaction of [(nbd)RhCl]2, Ph2P(m-NaOSO2C6H4) and Ph2CC(Ph)Li, whose structure was determined by NMR and IR spectroscopies. The Rh catalyst 1 induced the polymerization of phenylacetylene (PA) in water to give two kinds of polymers; one was soluble in organic solvents such as tetrahydrofuran (THF) and CHCl3, and the other was insoluble in common organic solvents. The polymerization of sodium p-ethynylbenzoate (p-NaOCO-PA) homogeneously proceeded with 1 in water at 60 °C to give the polymer in high yield. Poly(p-NaOCO-PA) was treated with 1 N HCl and then reacted with (CH3)3SiCHN2 to obtain poly(p-MeOCO-PA). The methyl-esterified polymer was insoluble in THF and CHCl3, which suggests that the formed poly(p-MeOCO-PA) has cis–cisoidal structure. The polymer obtained from the polymerization of [p-CH3(OCH2CH2)2O2CC6H4]CCH with 1 in water was soluble in methanol, ethanol, and THF, and partly soluble in water. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2100–2105, 2004

Keiji Kanki

Papers

Living polymerization of phenylacetylene by rhodium‐based ternary catalysts, (diene)Rh(I) complex/vinyllithium/phosphorus ligand. Effects of catalyst components

Remarkable cocatalytic effect of organometallics and rate control by triphenylphosphine in the Rh-catalyzed polymerization of phenylacetylene

Synthesis of a conjugated star polymer and star block copolymers based on the living polymerization of phenylacetylenes with a rh catalyst

Synthesis of poly(phenylacetylene)-block-poly(β-propiolactone) by use of Rh-catalyzed living polymerization of phenylacetylene

Polymerization of substituted phenylacetylenes with a novel, water‐soluble Rh–vinyl complex in water