Kotaro Satoh

Stereospecific living radical polymerization: dual control of chain length and tacticity for precision polymer synthesis.

3.3.3. Ionic Bonding or Interaction 5141 3.3.4. Multiple Hydrogen Bonding Interactions 5142 4. Stereospecific Living Radical Polymerization 5143 4.1. Acrylamides and Methacrylamides 5143 4.2. Methacrylates and Acrylates 5146 4.3. Vinyl Esters, Vinyl Amides, and Vinyl Chloride 5148 4.4. Stereoblock and Stereogradient Polymers 5149 4.4.1. Stereoblock Polymers 5149 4.4.2. Stereogradient Polymers 5151 5. Conclusions 5151 6. Acknowledgments 5152 7. References 5152

AAB-Sequence Living Radical Chain Copolymerization of Naturally Occurring Limonene with Maleimide: An End-to-End Sequence-Regulated Copolymer

Sequence control in chain-growth polymerization is still one of the most challenging topics in synthetic polymer chemistry in contrast to natural macromolecules with completely sequence-regulated structures like proteins and DNA. Here, we report the quantitative and highly selective 1:2 sequence-regulated radical copolymerization of naturally occurring (+)-d-limonene (L) and a maleimide (M) in fluoroalcohol giving chiral copolymers with high glass transition temperatures (220-250 degrees C) originating from the specific rigid cyclic structures of the monomers. Furthermore, the combination with a reversible addition-fragmentation chain transfer (RAFT) agent (C-S) via the controlled/living radical polymerization resulted in end-to-end sequence-regulated copolymers [C-(M-M-L)(n)-M-S] with both highly sequenced chain ends and main-chain repeating units as well as controlled molecular weights.

Sequence-regulated vinyl copolymers by metal-catalysed step-growth radical polymerization.

Proteins and nucleic acids are sequence-regulated macromolecules with various properties originating from their perfectly sequenced primary structures. However, the sequence regulation of synthetic polymers, particularly vinyl polymers, has not been achieved and is one of the ultimate goals in polymer chemistry. In this study, we report a strategy to obtain sequence-regulated vinyl copolymers consisting of styrene, acrylate and vinyl chloride units using metal-catalysed step-growth radical polyaddition of designed monomers prepared from common vinyl monomer building blocks. Unprecedented ABCC-sequence-regulated copolymers with perfect vinyl chloride-styrene-acrylate-acrylate sequences were obtained by copper-catalysed step-growth radical polymerization of designed monomers possessing unconjugated C=C and reactive C-Cl bonds. This strategy may open a new route in the study of sequence-regulated synthetic polymers.

Beyond Traditional RAFT: Alternative Activation of Thiocarbonylthio Compounds for Controlled Polymerization

Recent developments in polymerization reactions utilizing thiocarbonylthio compounds have highlighted the surprising versatility of these unique molecules. The increasing popularity of reversible addition–fragmentation chain transfer (RAFT) radical polymerization as a means of producing well‐defined, ‘controlled’ synthetic polymers is largely due to its simplicity of implementation and the availability of a wide range of compatible reagents. However, novel modes of thiocarbonylthio activation can expand the technique beyond the traditional system (i.e., employing a free radical initiator) pushing the applicability and use of thiocarbonylthio compounds even further than previously assumed. The primary advances seen in recent years are a revival in the direct photoactivation of thiocarbonylthio compounds, their activation via photoredox catalysis, and their use in cationic polymerizations. These synthetic approaches and their implications for the synthesis of controlled polymers represent a significant advance in polymer science, with potentially unforeseen benefits and possibilities for further developments still ahead. This Research News aims to highlight key works in this area while also clarifying the differences and similarities of each system.

Biomass-derived heat-resistant alicyclic hydrocarbon polymers: poly(terpenes) and their hydrogenated derivatives

Naturally-occurring terpenes, such as (−)-β-pinene and (−)-α-phellandrene, were cationically polymerized and subsequently hydrogenated into stable alicyclic hydrocarbon polymers with a rigid backbone. In contrast to the already known poly(terpenes), the hydrogenated poly(β-pinene) with a high molecular weight (Mw > 50 000) showed a high glass transition temperature (Tg = 130 °C) and degradation temperature (10% loss at > 400 °C), suggesting new promising biomass-derived materials for practical use.

Design and synthesis of self-degradable antibacterial polymers by simultaneous chain- and step-growth radical copolymerization

Self-degradable antimicrobial copolymers bearing cationic side chains and main-chain ester linkages were synthesized using the simultaneous chain- and step-growth radical polymerization of t-butyl acrylate and 3-butenyl 2-chloropropionate, followed by the transformation of t-butyl groups into primary ammonium salts. We prepared a series of copolymers with different structural features in terms of molecular weight, monomer composition, amine functionality, and side chain structures to examine the effect of polymer properties on their antimicrobial and hemolytic activities. The acrylate copolymers containing primary amine side chains displayed moderate antimicrobial activity against E. coli but were relatively hemolytic. The acrylate copolymer with quaternary ammonium groups and the acrylamide copolymers showed low or no antimicrobial and hemolytic activities. An acrylate copolymer with primary amine side chains degraded to lower molecular weight oligomers with lower antimicrobial activity in aqueous solution. This degradation was due to amidation of the ester groups of the polymer chains by the nucleophilic addition of primary amine groups in the side chains resulting in cleavage of the polymer main chain. The degradation mechanism was studied in detail by model reactions between amine compounds and precursor copolymers.

Precision synthesis of bio-based acrylic thermoplastic elastomer by RAFT polymerization of itaconic acid derivatives.

Bio-based polymer materials from renewable resources have recently become a growing research focus. Herein, a novel thermoplastic elastomer is developed via controlled/living radical polymerization of plant-derived itaconic acid derivatives, which are some of the most abundant renewable acrylic monomers obtained via the fermentation of starch. The reversible addition-fragmentation chain-transfer (RAFT) polymerizations of itaconic acid imides, such as N-phenylitaconimide and N-(p-tolyl)itaconimide, and itaconic acid esters, such as di-n-butyl itaconate and bis(2-ethylhexyl) itaconate, are examined using a series of RAFT agents to afford well-defined polymers. The number-average molecular weights of these polymers increase with the monomer conversion while retaining relatively narrow molecular weight distributions. Based on the successful controlled/living polymerization, sequential block copolymerization is subsequently investigated using mono- and di-functional RAFT agents to produce block copolymers with soft poly(itaconate) and hard poly(itaconimide) segments. The properties of the obtained triblock copolymer are evaluated as bio-based acrylic thermoplastic elastomers.

Stereogradient Polymers Formed by Controlled/Living Radical Polymerization of Bulky Methacrylate Monomers

Life RAFT: A bulky methacrylate monomer, triphenylmethyl methacrylate (TrMA), was polymerized with reversible addition-fragmentation chain transfer (RAFT) agents. Stereogradient polymers in which the isospecificity increased spontaneously as the monomer concentration decreased were formed by a polymerization-depolymerization equilibrium that can convert a less stable growing polymer terminal into a more stable form (see picture).

Sulfonic acids as water-soluble initiators for cationic polymerization in aqueous media with Yb(OTf)(3)

Aqueous sulfonic acids (HOSO2R; R = CH3, Ph-p-CH3, and Ph-p-NO2), coupled with a water-tolerant Lewis acid, ytterbium triflate [Yb(OTf)3; OTf = OSO2CF3], initiate the cationic suspension polymerization of p-methoxystyrene (pMOS) in heterogeneous aqueous media. They induce controlled polymerization of pMOS at 30 °C, and the molecular weights of the polymers (weight-average molecular weight/number-average molecular weight ∼ 1.7) increase with conversion. These suspension polymerizations are initiated by the entry of sulfonic acid from the aqueous phase into the organic phase and proceed via reversible activation of the sulfonyl terminus by the Lewis acid.

Interconvertible Living Radical and Cationic Polymerization through Reversible Activation of Dormant Species with Dual Activity

The polymerization of vinyl monomers generally requires the selection of an appropriate single intermediate, whereas in copolymerization, the selection of the comonomer is limited by the intermediate. Herein, we propose interconvertible dual active species that can connect comonomers through different mechanisms to produce specific comonomer sequences in a single polymer chain. More specifically, two different stimuli, that is, a radical initiator and a Lewis acid, are used to activate the common dormant C-SC(S)Z group into radical and cationic species, thereby inducing interconvertible radical and cationic copolymerization of acrylate and vinyl ether to produce a copolymer chain that consists of radically and cationically polymerized segments. The dual reversible activation provides control over molecular weights and multiblock copolymers with tunable segment lengths.