Investigation of the Locked-Unlocked Mechanism in Living Anionic Polymerization Realized with 1-(Tri-isopropoxymethylsilylphenyl)-1-phenylethylene

Synthesis of α,ω-End Functionalized Polydienes: Allylic-Bearing Heteroleptic Aluminums for Selective Alkylation and Transalkylation in Coordinative Chain Transfer Polymerization

There are still challenges in the preparation of difunctional stereoregular polydienes, especially for the construction of initiating chain-end functionalization. Coordinative chain transfer polymerization (CCTP) provides a way to achieve the goal but usually requires sophisticated functionalized catalysts as well as expensive chain transfer agents (CTAs). In this work, heteroleptic aluminum with oligo(dienyl) substituents (oligo-Al agents) were readily prepared by living anionic polymerization (LAP) technique. The oligo-Al agents used in Nd-mediated CCTPs of dienes exhibit highly selective alkylation and transalkylation features. Kinetics and transfer efficiency studies using 1 H NMR, 13 C NMR, 1 H-13 C HSQC, and Dosy NMR analyses revealed that the resulting polydienes possess substituents at the initiating chain-end that have transferred from the oligo-Al agents. The functionalization efficiency of the initiating chain-end is up to 99 %, and the molar mass regulation efficiency of heteroleptic aluminum is higher than that of the traditional CTA Ali Bu2 H (0.608 vs. 0.410). Based on the experimental results and density functional theory (DFT) calculations, we propose a mechanism in which allylic-Al acts as an efficient alkylating moiety in catalyst preformation and also as an effective transfer agent in polymerization. Taking advantage of these features, di-functionalized polyisoprene, polybutadiene, and poly(isoprene-co-butadiene) can be facilely synthesized.

Ketyl Radical Anion Mediated Radical Polymerization and Anionic Ring-Opening Polymerization to Give Polymers with Low Molecular Weight Distribution

The development of novel polymerization capable of yielding polymers with low molecular weight distribution (Đ) is essential and significant in polymer chemistry, where monofunctional initiator contains only one initiation site in these polymerizations generally. Here, ketyl radical anion species is introduced to develop a novel Ketyl Mediated Polymerization (KMP), which enables radical polymerization at carbon radical site and anionic ring-opening polymerization at oxygen anion site, respectively. Meanwhile, polymerization and corresponding organic synthesis generally couldn't be performed simultaneously in one pot. Through KMP, organic synthesis and polymerization are achieved in one pot, where small molecules (cyclopentane derivates) and polymers with low Đ are successfully prepared under mild condition simultaneously. At the initiation step, both organic synthesis and polymerization are initiated by single electron transfer reaction with ketyl radical anion formation. Cyclopentane derivates are synthesized through 3-3 coupling reaction and cyclization. Polystyrene and polycaprolactone with low Đ and a full monomer conversion are prepared by KMP via radical polymerization and anionic ring-opening polymerization, respectively. This work therefore enables both organic synthesis and two different polymerizations from same initiation system, which saves time, labour, resource and energy and expands the reaction mode and method libraries of organic chemistry and polymer chemistry.

Quo Vadis Carbanionic Polymerization?

Living anionic polymerization will soon celebrate 70 years of existence. This living polymerization is considered the mother of all living and controlled/living polymerizations since it paved the way for their discovery. It provides methodologies for synthesizing polymers with absolute control of the essential parameters that affect polymer properties, including molecular weight, molecular weight distribution, composition and microstructure, chain-end/in-chain functionality, and architecture. This precise control of living anionic polymerization generated tremendous fundamental and industrial research activities, developing numerous important commodity and specialty polymers. In this Perspective, we present the high importance of living anionic polymerization of vinyl monomers by providing some examples of its significant achievements, presenting its current status, giving several insights into where it is going (Quo Vadis) and what the future holds for this powerful synthetic method. Furthermore, we attempt to explore its advantages and disadvantages compared to controlled/living radical polymerizations, the main competitors of living carbanionic polymerization.

Living Covalent-Anionic-Radical Polymerization via a Barbier Strategy

The developments of the living alkene polymerization method have achieved great progress and enabled the precise synthesis of important polyalkenes with controlled molecular weight, molecular weight distribution, and architecture through an anionic, cationic or radical strategy. However, it is still challenging to develop a living alkene polymerization method through an all-in-one strategy where anionic and radical characteristics are merged into one polymerization species. Here, a versatile living polymerization method is reported by introducing a well-established all-in-one covalent-anionic-radical Barbier strategy into a living polymerization. Through this living covalent-anionic-radical Barbier polymerization (Barbier CARP), narrow distributed polystyrenes, with Đ as low as 1.05, are successfully prepared under mild conditions with a full monomer conversion by using wide varieties of organohalides, for example, alkyl, benzyl, allyl, and phenyl halides, as initiators with Mg in one pot. This living covalent-anionic-radical polymerization via a Barbier strategy expands the methodology library of polymer chemistry and enables living polymerization with an unconventional polymerization mode.

Determination of refractive index increment of synthetic polybutadienes and microstructural control of grafting density and liquid crystalline properties

Polybutadienes (PBs) with microstructural control of 8% to 94% moles of 1,2-olefins synthesizedvialiving anionic polymerization (LAP) were used as precursors for the synthesis of PB-based liquid crystalline polymers (LCPs) with well-controlled grafting densities.

Sequence regulation in living anionic terpolymerization of styrene and two categories of 1,1-diphenylethylene (DPE) derivatives

In living anionic polymerization, gradient, block and random sequences of two categories of DPE derivatives were easily generated by implementing different feed strategies and screening the DPE derivative pairs with different reactivities.

Regulation of cis and trans microstructures of isoprene units in alternating copolymers via “space-limited” living species in anionic polymerization

Space-limited living species provide new insight into the regulation of the microstructure of isoprene units in alternating copolymers composed of isoprene and 1,1-bis(4-dimethylsilylphenyl)ethylene (DPE-2SiH).

Unlocking features of locked-unlocked anionic polymerization

Unlocking features of the locked-unlocked anionic polymerization were investigated and reported.

Synthesis of monodisperse isomeric oligomers based on meta-/para- and linear/star-monomer precursors with Ugi–hydrosilylation orthogonal cycles

Monodisperse oligomers were precisely prepared through orthogonal cycles of Ugi-4CRs and hydrosilylation coupling reactions, and the “monodisperse isomeric oligomers” were explored.

Synthesis of strictly alternating copolymers by living carbanionic copolymerization of diphenylethylene with 1,3-pentadiene isomers

The living carbanionic alternating copolymerizations of 1,3-pentadiene isomers with DPE are reported, and yield well-defined alternating and highly stereoregular amorphous copolymers with controllable M_n, low Đ_M and predominantly trans-1,4 units.