This report describes the synthesis of a series of sodium complexes bearing cavity-like conformations formed with the aid of sterically hindered phenoxide and 15-crown-5 ether ligands. All the complexes are well-characterized via NMR spectroscopy analysis, and through single crystal X-ray studies and DFT calculations it is found that the size of the cavity is very similar to that of macrolactone monomers. During subsequent studies of the ring-opening polymerization (ROP) of macrolactones, the present sodium complexes demonstrate high catalytic efficiencies in the ROP of pentadecalactone and ethylene brassylate, affording the corresponding polyester products in high yields. Moreover, due to chain propagation being confined within the cavity, transesterification can be suppressed because of mutual steric repulsion between the ligands and polymer chains, which further allows polymerization to proceed in a well-controlled manner. Owing to such uniqueness, block copolymerization between macrolactones and other cyclic esters can be also successfully achieved.

A highly efficient late-transition metal based catalytic system of α-diimine FeCl₃ for well-controlled ring opening polymerization of a cheap and biobased macrolactone, ethylene brassylate (EB), is described herein.

Tapping facile and efficient strategies for preparing α,ω-end hetero-functionalized polyisoprene (PIp) that mimics the chain structure of natural rubber (NR) has been a long-standing pursuit in polymer science. In this study, we present a novel approach utilizing neodymium-catalyzed coordinative chain transfer polymerization (CCTP) to construct end-functionalized PIps with distinct functional groups at the α- and ω-termini. The α-end functionalization was achieved by incorporating copolymerizable heteroatomic 1-substituted dienes (Bd_PhX) during the aging stage of polymerization. By varying the type and feed ratio of Bd_PhX, a diverse array of α-functional moieties with tunable incorporation levels was readily obtained. Detailed kinetic studies revealed that the presence of α-functional Bd_PhX moieties exerted minimal impact on the CCTP process, maintaining highly reactive allyl–metal bonds (predominantly allyl–Al bonds) crucial for subsequent ω-end functionalizations. The ω-end functionalization was realized through two complementary strategies: (1) the incorporation of copolymerizable diene derivatives and (2) in situ reactions with reactive small molecules. The first approach was achieved by introducing Bd_PhX monomers, while in the second approach, reactive small molecules such as isothiocyanates and oxygen, were employed to construct thioamide and hydroxyl end-functional groups, respectively. The synthesized polymers were comprehensively characterized to confirm their structures and functionalities, highlighting the versatility and efficiency of this strategy for designing α,ω-end hetero-functionalized PIps.

The Nd-mediated coordinative chain transfer polymerization (CCTP) of dienes represents one of the state-of-the-art techniques in the current synthetic rubber field. Besides having well-controlled polymerization behaviors as well as high atom economies, it also allows for the generation of highly reactive Al-capped polydienyl chain-ends, which hold great potential, yet much less explored up to date, in achieving end functionalization to mimic the structure of natural rubber. In this study, we demonstrate an efficient in situ method to realize end-functionalizing polyisoprene by introducing epoxide compounds into a CCTP system. The end functionalization efficiency was 92.7%, and the obtained polymers were systematically characterized by 1H NMR, 1H,1H-COSY NMR, DOSY NMR, and MALDI TOF. NMR studies revealed that a maximum of two EO units were introduced to the chain ends, and based on density functional theory (DFT) studies, an energy barrier of 33.3 kcal/mol was required to be overcome to open the ring of the EO monomer. Increasing the ratio of [Ip]/[Nd] resulted in gradually increased viscosities for the reaction medium and therefore gave rise to an end functionalization efficiency that decreased from 92.7% to 74.2%. The end hydroxyl group can also be readily converted to other functionalities, as confirmed by NMR spectroscopy.

Copolymerization of 1,3-butadiene with various types of phenyl substituted 1,3-butadiene derivatives, including (E)-1-phenyl-1,3-butadiene (PBD), 1-phenethyl-1,3-butadiene (PEBD), 1-(4-methoxylphenyl)-1,3-butadiene (p-MEPBD), 1-(2-methoxylphenyl)-1,3-butadiene (o-MEPBD) and 1-(4-N,N-dimethylaminophenyl)-1,3-butadiene (p-DMPBD), by using a coordination polymerization system of CpTiCl₃/MAO is reported herein. Comonomers PBD and PEBD can be copolymerized with 1,3-butadiene in a large range of comonomer feed ratios (0–44.6% for PBD, 0–30.2% for PEBD), affording the targeted copolymers with well-controlled comonomer incorporations, molecular weights, polydispersities and microstructure, whereas no corresponding copolymer products were obtained under identical conditions when p-MEPBD, o-MEPBD and p-DMPBD were employed. Moreover, different polymerization parameters, including temperature, Al/Ti ratio, etc., posed a significant influence on the polymerization behaviors, as well as the properties of the resultant copolymers. Microstructure analysis by NMR spectra revealed high 1,4-selectivities of the catalysts, and the glass transition temperature (T_g) of the resulted copolymer was found to be highly dependent on the incorporation content of the comonomers; with an increasing comonomer content, a gradually increasing T_g was demonstrated.

Coordination chain transfer polymerization (CCTP) has emerged as an efficient and controllable polymerization strategy that also allows for efficient in situ end-functionalization of polydienes through the highly reactive metal–carbon bonds that are generated during the CCTP process. Despite substantial progress in CCTP chemistry, reviews focusing specifically on its application to diene monomers—and particularly on its effectiveness in producing end-functionalized polydiene elastomers—remain scarce. To address this gap, this review summarizes the advances achieved over the past decade in the end-functionalization of polydienes via CCTP. We begin with a brief overview of the fundamental principles and core mechanisms of CCTP, followed by a systematic discussion of functionalization strategies for key diene monomers, including isoprene and butadiene. Finally, we highlight the existing challenges in this field and provide our perspectives on future research directions.