| POLYMERS Vol.68 No.2 |
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COVER STORY
Innovative Methodologies for Polymer Synthesis |
| COVER STORY: Highlight Reviews |
| Design of Polymerization Catalysts Based on Dinuclear Transition Metal Complexes | Daisuke TAKEUCHI |
| <Abstract> Recent examples of dinuclear transition metal complex catalysts for olefin polymerization are described. Dinculear transition metal complex catalysts have been known to often show higher catalytic activity and/or afford polymers with higher molecular weight, compared to the mononuclear analogue, in olefin polymerization. Recently, various dinuclear complexes with short metal-metal distance having rigid structure and/or two different metal centers were designed. Those newly-designed dinuclear complexes enable some new polymerizations, which were difficult to be realized by using mononuclear complexes. Heterodinuclear complex catalysts composed of one metal center, active in ethylene oligomerization, and the other, active in ethylene/α-olefin copolymerization, allow tandem polymerization of ethylene resulting in polyethylene with controlled branched structure in one pot. Keywords: Metal-Catalyzed Polymerization / Dinuclear Catalyst / Transition Metal Catalyst / Olefin Polymerization / Copolymerization / Tandem Polymerization |
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| Polymer Synthesis via Metal-Catalyzed C-H Activation | Masayoshi NISHIURA, Zhaomin HOU |
| <Abstract> This article describes recent advances in metal-catalyzed C-H bond activation for polymer synthesis. C-H polyaddition to unsaturated C-C bonds has led to the formation of a new family of alternating copolymers in an atom- and step-economical fashion. Olefin polymerization via C-H activation as a chain transfer reaction has afforded end-functionalized polyolefins with 100％ atom-efficiency. Keywords: Rare Earth Metal / Ruthenium / C-H Polyaddition / Alternating Copolymerization / Chain Transfer Polymerization / Step-Growth Polymerization |
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| Cyclocopolymerization Based on Alternative Insertions of Isocyanide and Unsaturated Hydrocarbons into a Palladium-Carbon Bond | Naoya KANBAYASHI, Kiyotaka ONITSUKA |
| <Abstract> The insertion reaction of isocyanide into metal-carbon bonds is among the fundamental reactions in organometallic chemistry, and the unique reactivity has been applied to the synthesis of polyisocyanide using organometallic complexes as an initiator. However, these polymerizations were limited to homopolymerization of isocyanides. Recently, a novel type of copolymerization of isocyanides and other type of monomers has been studied for the synthesis of polymers having a new type of primary structure. In this review, new mode of polymerizations of isocyanide through the alternative insertion of isocyanide and unsaturated hydrocarbons is described. Keywords: Isocyanide / Organopalladium Complex / Alternative Insertion / Allene / Alkyne / Coordination Polymerization / Cyclocopolymerization / Living Polymerization |
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| COVER STORY: Topics and Products |
| Polymer Synthesis using N-Heterocyclic Carbene as the Initiator | Akinori TAKASU |
| <Abstract> A diene-based cyclic polymer has been synthesized by the anionic polymerization of methyl sorbate (MS) by an N-heterocyclic carbene (NHC). Although the polymerization did not occur in toluene in the absence of any additive, quantitative monomer consumption was observed in the presence of methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) (MAD) to afford the poly(MS) with a 1,4-trans structure, 86％ of threo diastereoselectivity, and a Mn of 23.0×103 with narrow molecular weight distribution (Mw/Mn = 1.17). From the matrix assisted laser desorption/ionization (MALDI-TOF) mass spectra of poly(MS) and the hydrogenated analogue, ring-closing occurred by nucleophilic attack of the anionic propagating center into the adjacent carbon of the α-terminal imidazolimium group to afford cyclic poly(MS). In this paper, we introduced NHC-initiated ring-opning polymerization of racemic lactide to give stereoregular not cyclic but linear poly(lactide) in the presence of MAD. Keywords: N-Heterocyclic Carbene (NHC) / Cyclic Polymer / Ring-Clossure Procedure without Highly Diluted Condition / Alkyl Sorbate / Lactide / Stereoregularity |
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| Construction, Destruction, and Transformation of Polymer Main Chain by Conjugate Substitution of α-(Halomethyl)acrylates | Yasuhiro KOHSAKA |
| <Abstract> Conjugate substitution of α-(halomethyl)acrylates is an attractive reaction for polymerization, polymer degradation and modification, because it affords α-functionalized acrylates with quantitative yields under ambient condition. For example, bis[α-(chloromethyl)acrylate] underwent polycondensation with bisphenols, dicarboxylic acids, primary monoamines, and dithiols to yield the corresponding poly(conjugated esters). Among them, the polymers prepared from dicarboxylic acids were degradable by the treatment with thiols, as the α-(acyloxymethyl)acrylate skeletons in the backbone is also active to conjugate substitution. In a similar mechanism, the poly(ester ester) were converted to poly(ester sulfide) through the conjugate substitution with dithiols. The conversion approximately agreed with the feed ratio of dithiols against the α-(acyloxymethyl)acrylate skeletons. Since conjugate substitution proceeds under mild conditions, the reaction is compatible to other nucleophilic reactions. α-(Chloromethyl)acryloyl chloride that can accept both conjugate substitution and acyl substitution was polymerized with dicarbonyl chlorides and bisphenols, resulting in polyacylate with α-(acyloxymethyl)acrylate skeletons. The polycondensation of α-(bromomethyl)acrylate and dithiols was achieved by the combination of conjugate substitution and addition reactions. Keywords: Conjugate Substitution / α-(Halomethyl)acrylates / Poly(conjugated ester)s / Polycondensation / Tandem Reaction / Domino Reaction / Polymer Degradation / Main Chain Transformation |
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| Catalyst Design Holds the Key to the Next-Generation Tire Materials | Shojiro KAITA |
| <Abstract> Due to technology innovations, future direction of mobility will change significantly, such as to electric vehicles (EV)･fuel cell vehicles (FCV) and autonomous vehicles. Following this trend, demand for next generation tires will also diversify. Focusing on “long life / high strength tire”, which is one of the most important tasks for realizing the future mobility society, it is necessary to develop new high value tire materials (e.g., new rubber materials). Here, we will report the creation of two novel polymers using our “novel polymerization catalyst”, a new isoprene rubber with precise molecular structure and a polymer having rubber and resin at a molecular level for the first time. Keywords: Polymerization Catalyst / Future Mobility / High Strength / New Rubber Materials / Isoprene Rubber / Rubber and Resin |
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| Polymer Synthesis with Multi-Component Reactions | Ryohei KAKUCHI |
| <Abstract> This manuscript highlights a new stream in polymer chemistry, which is essentially taking advantage of the synthetic utility of multi-component reactions (MCRs). For example, the author has been showing the synthetic benefits of the Kabachnik-Fields (KF) reaction. The KF reaction was dicoverd in 1950s and refers to the reaction among amines, aldehydes, and phosphonates to afford the corresponding α-aminophosphonate esters. Despite the fruitful features of the KF reaction, the KF reaction had not been incorporated into polymer science until very recently. The author has merged the KF reaction as an elementary reaction in polymer science, with which facile post polymerization functionalization and a step growth polymerization were realized to access a wide range of polymeric α-aminophosphonate esters. Keywords: Postmodification / Polycondensation / Multicomponent Reaction / Biomass |
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| Polymer Science and I: A Personal Account |
| Coping Ability Training | Eiji YUBA |
| <Abstract> This essay describes the relationship between my experiences and current research topics about polymer-based immunity-inducing systems. Various occurrences in my life provided me with the coping ability to manage the research. Especially, the experience in drug eruption strongly affected me to be interested in control of immunological reactions by synthetic molecules. |
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| Front-Line Polymer Science |
| Living Anionic Polymerization～Development of New Monomers | Takashi ISHIZONE, Raita GOSEKI |
| <Abstract> The living anionic polymerization is a promising way for synthesis of well-defined polymers since discovered by Szwarc in 1956. Recently, intrigued chain-end functionalized polymers and architectural polymers such as multiblock copolymer, star-shaped polymer, and graft polymer are also synthesized precisely by taking advantage of “living” nature of the chain-end anion. Nowadays, a wide variety of monomers can be utilized for the living anionic polymerization, although there has been a limit in the anionic polymerizable monomer due to the high reactivity of the anionic species. Recent progress on the new initiator systems, suitable design of monomer structures, and effective stabilization of the propagating anion with additives enables to significantly expand the range of monomers. Those novel designed attractive monomers include divinylbenzenes, adamantane containing vinyl monomers, exomethylene monomers, functional (meth)acrylates, (meth)acrylamides, and cyclic monomers. In this review, we highlight recent advances of the living anionic polymerization, particularly recent developed monomers showing anionic polymerizability. Keywords: Living Anionic Polymerization / Block Copolymers / Styrene Derivatives / Divinyl Benzenes / Adamantane Containing Vinyl Monomers / Exomethylene Monomers / Diene Derivatives / Polar Monomers / Cyclic Monomers |
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