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The eco-environmentally PVLs without catalyst-residue have been facilely synthesized using heterogeneous PS- t -BuP 2 catalyst by simple filtration and without tedious purification process. • The heterogeneous catalyst PS- t -BuP 2 was employed for ROP of δ -VL. • PS- t -BuP 2 is easily recovered and reusable for five cycles without deactivation. • PVLs without catalyst-residue are synthesized using PS- t -BuP 2 by simple filtration. We demonstrated that the dimeric 1- tert -butyl-2,2,4,4,4-pentakis(dimethylamino)-2Λ5, 4Λ5-catenadi(phosphazene) supported on polystyrene (PS- t -BuP 2 ) was an efficient and recyclable catalyst for the ring-opening polymerization (ROP) of δ -valerolactone (δ -VL). The heterogeneous catalyst PS- t -BuP 2 could be recycled and reused for five consecutive cycles without significant decrease of catalytic activity. The monomer conversions maintained between 79% and 85% for five cycles. Using BnOH as initiator, the produced polyvalerolactones (PVLs) had controlled molecular weights (MWs) and narrow MW distributions (Đ), and the products were free of catalyst by simple filtration. The 1H NMR and MALDI-TOF characterizations of the obtained PVLs clearly indicated the presence of the initiator residue at the chain end. [ABSTRACT FROM AUTHOR]

Graphical abstract The binary organocatalytic system comprised of CTPB and ureas is developed and shows both of high activity and selectivity for the ROP of cyclic esters. Highlights • A simple and synergetic binary catalytic system containing CTPB and urea has been developed. • The ROP of ε -CL and δ -VL was highly controlled. • The linear and three-arm star block copolymers were readily prepared. • The synergetic bifunctional mechanism was investigated. Abstract Phosphazenes have attracted considerable attention in the field of ring-opening polymerization (ROP) of cyclic esters. However, the application of phosphazenes as catalyst is subject to a trade-off between activity and selectivity (chain propagation versus transesterification/back-biting reaction, e.g., controlled polymerization). Despite extensive research efforts, the development of a new catalytic system having concurrent high activity and selectivity remains a great challenge. In this work, we report that the binary organocatalytic system comprised of cyclic trimeric phosphazene base (CTPB) and ureas shows both of high activity and selectivity for the ROP of ε -caprolactone (ε -CL) and δ -valerolactone (δ -VL) in the presence of alcohol as initiator. It is found that the introduction of ureas would significantly increase the catalytic selectivity during ROP without sacrificing the catalytic activity of CTPB. Moreover, the polymerizations catalyzed by the title catalytic system exhibit immortal characteristics and thus thousands equivalent of monomer could be converted to polymer efficiently with desired MWs and microstructures. Linear diblock copolymer AB and star copolymers (AB) 3 with three identical diblock arms could be readily synthesized by sequential copolymerization using different alcohols as initiators. [ABSTRACT FROM AUTHOR]

Al complexes bearing amino-quinoline ligands rapidly converted hundreds even thousands equiv. of ε-CL into PCLs with high conversions in a living and/or immortal manner. [Display omitted] • A series of Al complexes (Al1 − Al5) bearing N,N-bidentate amino-quinoline ligands were synthesized and fully characterized. • Al complexes Al1 − Al5 could catalyze fast and living ring-opening polymerization (ROP) of ε -caprolactone (ε -CL). • Polycaprolactones (PCLs) with high molecular weights (M n up to 129 kDa) and narrow dispersity (Đ = 1.16) were readily synthesized. • An extremely low loading of Al complex (0.05 mol% to ε -CL monomer) was efficient for ROP of ε -CL to prepare PCL with desired M n and narrow distribution in an immortal manner. Catalysts drive innovation in sustainable polymers because of their reactivity and selectivity. In this context, the synthesis and characterization of a series of Al complexes (Al1 − Al5) bearing N,N-bidentate amino-quinoline ligands are described, as well as their applications in ring-opening polymerization (ROP) of ε -caprolactone (ε -CL). The amido-coordination Al complexes were directly synthesized by reactions of imino-quinoline compounds with AlMe 3 via methyl migration from Al to the carbon atom of imine, as indicated by both NMR spectroscopy and X-ray diffraction. In the presence of BnOH, complexes Al1 − Al5 showed significant reactivity for ROP of ε -CL with good control over molar mass (M n) and dispersity (Đ < 1.2), and polycaprolactones (PCLs) with high molecular weights (M n up to 129 kDa) were readily synthesized. Remarkably, immortal catalysis with excess of BnOH (up to 20 equiv. to Al) was achieved to prepare PCLs with predictable M n s, low dispersities, and end groups using an extremely low loading of Al complex (0.05 mol% to ε -CL monomer). [ABSTRACT FROM AUTHOR]

Self-healing polyester elastomers with good mechanical strength, excellent toughness and rapid self-healing property were obtained by post-functionalized polyester backbone with UPy units through a thiol-ene click reaction. [Display omitted] • Self-healing polyester elastomers were obtained by post-functionalized polyester backbone with UPy units. • Elastomers show good mechanical strength, excellent elongation at break, good toughness and rapid self-healing property. • High polyester molecular weight, moderate UPy content and inhibition of crystallization are helpful to improve the mechanical and self-healing properties of elastomers. It is a desirable to prepare high performance polyester elastomers that possess high strength, good elasticity and efficient self-healing capability. Herein, we report the preparation of such elastomers based on aliphatic polyesters cross-linked by UPy-UPy quadruple hydrogen bonding. A functional monomer α-methylene-γ-butyrolactone (MBL) was copolymerized with ε-caprolactone (ε-CL) to give pendent double bonds functionalized copolyester precursors, which were subject to post-modification with UPy groups via the efficient thiol-ene click reaction. Then, the self-healing polyester elastomers were finally obtained by tuning the molecular weight of precursors, the contents of UPy units and crystallization behaviors. The results show that high polyester molecular weight, moderate UPy content and inhibition of crystallization are helpful to improve the mechanical and self-healing properties of elastomers. The obtained elastomers show good mechanical strength (1.0–1.5 MPa), excellent elongation at break (970–1560 %) and toughness (9.6–11.9 MJ/m3), and have the rapid self-healing property (>70 % after healing at 60 °C for 2 h), displaying great potential in biomedical applications. [ABSTRACT FROM AUTHOR]

High molecular weights polydiethylsiloxanes and random poly(dimethylsiloxane-co-diethylsiloxane) copolysiloxanes were synthesized via cyclic trimeric phosphazene base catalyzed ring-opening (co)polymerization at room temperature. [Display omitted] • PDES homopolymers, with molecular weight up to 404.0 kg/mol, were conveniently synthesized at room temperature within 4 hrs using CTPB as catalyst. • High molecular weight random copolymers of diethylsiloxane with different dimethylsiloxane contents were successfully prepared within 5 min at room temperature in high yields. • Reactivity ratio determination experiments suggested that the ROCP of D 3 Et with D 4 mediated by CTPB proceeded in a fully random manner, demonstrating the high catalytic activity of CTPB. Polysiloxanes containing diethylsiloxane units with unique low temperature flexibility have been widely applied under extreme conditions in many fields. However, the synthesis of polydiethylsiloxane (PDES) and its copolymers was challenging due to the easy accessible polymerization-depolymerization equilibrium between linear propagating chains and cyclosiloxane byproducts in the ring-opening polymerization (ROP) of hexaethylcyclotrisiloxane (D 3 Et) and the large reactivity gaps among different cyclosiloxanes in the copolymerization. In this work, PDESs were successfully prepared via cyclic trimeric phosphazene base (CTPB) catalyzed ROP at room temperature in high yields. The ROP of D 3 Et proceeded efficiently with low CTPB loading (low to 0.01 mol%) and the resulting PDES homopolymers had high molecular weights (up to 404.0 kg/mol). Moreover, poly(dimethylsiloxane- co -diethylsiloxane) (PMES) random copolymers with tunable diethylsiloxane contents (20 ∼ 87 mol%) can be directly prepared via ring-opening copolymerization (ROCP) of D 3 Et and octamethylcyclotetrasiloxane (D 4) using CTPB as catalyst within 5 min at ambient temperature. The reactivity ratio of D 3 Et (r = 1.04) and D 4 (r = 0.89) suggested the comparable reactivity between D 3 Et and D 4 to ensure their random copolymerization characteristics, thus proving the unique high efficiency of CTPB catalyst applied here. Microstructure characterizations of the PMES copolymers by 1H and 29Si NMR verified the controlled copolymer composition and the random distribution of diethylsiloxane and dimethylsiloxane units. The thermal property investigations by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) indicated the good low-temperature flexibility and thermal stability of PMES copolymers, displaying great potential in extreme environmental applications. [ABSTRACT FROM AUTHOR]