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Borane‐based Lewis acids (LA) play an indispensable role in the Lewis pair (LP) mediated polymerization. However, most borane‐based LPs are moisture‐ and air‐sensitive. Therefore, development of moisture and air‐stable borane‐based LP is highly desirable. To achieve this goal, the concept of "aggregation induced enlargement effects" by chemically linking multiple borane within a nanoscopic confinement was conceived to create macromolecular LA. Accordingly, an extremely moisture and air stable macromolecular borane, namely, PVP‐1B featuring poly(4‐vinylphenol) backbone, was constructed. The concentration of borane active site is greatly higher than average concentration due to local confinement. Therefore, an enhanced activity was observed. Moreover, the local LA aggregation effects allow its tolerance to air and large amount of chain transfer agent. Consequently, PVP‐1B showed remarkable efficiency for propylene oxide (PO) polymerization at 25 °C (TOF=27900 h−1). Furthermore, it enables generation of well‐defined telechelic poly (CHO‐alt‐CO2) diol (0.6–15.3 kg/mol) with narrow Đs via copolymerizing cyclohexene oxide and CO2 at 80 °C. This work indicates unifying multiple borane within a polymer in a macromolecular level shows superior catalytic performance than constructing binary, bi(multi)functional systems in a molecular level. This paves a new way to make functional polyethers. [ABSTRACT FROM AUTHOR]

Supramolecular silicone elastomer is a promising material for sustainable development. Here, quadruple hydrogen bonded ureidopyrimidinone (UPy) units were grafted onto high molecular weight polydimethylsiloxanes (PDMS), providing a novel supramolecular silicone elastomer. The high molecular weight PDMS precursor was prepared through a cyclic trimeric phosphazene base catalyzed ring‐opening polymerization of Octamethylcyclotetrasiloxane (D4) and tetravinyltetramethylcyclotetrasiloxane (V4) with a well‐controlled vinyl content. Its side chains were modified by hydroxyl groups via a thiol‐ene reaction. Then UPy units were further grafted on the side chain of high molecular weight PDMS by the isocyanate‐hydroxy reaction. The mechanical and self‐healing properties of the elastomer can be controlled by adjusting the molecular weight of PDMS and the amount of UPy units. The obtained PDMS elastomers displayed excellent stretchability (elongation at break of 1513%), good self‐healing efficiency (76% at 60°C for 2 h), and high resilience (elastic recovery of 93% under 300% strain cyclic stretching). [ABSTRACT FROM AUTHOR]

Polylactide (PLA) is a fully bio‐derived polyester with great biodegradability, biocompatibility, and mechanical properties. Synthesis of stereoregular PLA by highly stereoselective organocatalyzed ring opening polymerization (ROP) of racemic lactide (rac‐LA) at room temperature is challenging despite some important developments in the past few years. In this contribution, two bulky phenyl diphosphazene bases, p‐PDPB and m‐PDPB, were conveniently synthesized by the Staudinger reaction. In combination with different hydrogen‐bond donors such as ureas and squaramides, they could mediate the stereocontrolled ROP of rac‐LA in THF at room temperature. Semicrystalline PLAs with narrow dispersity and high tacticity (Pm up to 0.84) were successfully synthesized in a well‐controlled manner using phenyl diphosphazene based/urea binary catalytic system. Structural analysis verified the linear structure and high end‐group fidelity of the resulting polymers. Moreover, the minimal transesterification of the polymer backbone proved by the MALDI‐TOF MS analysis indicated the good controllability of the phenyl diphosphazene based binary catalytic system. [ABSTRACT FROM AUTHOR]

Although great successes have been achieved, the preparation of closed‐loop recyclable polyesters with high working temperatures still remains as a big challenge. Herein, we present the syntheses of a series of enantiopure bicyclic ether‐ester monomers by upcycling of poly(3‐hydroxybutyrate) bioplastic. The "living"/controlled ring‐opening polymerizations of these enantiopure monomers to produce stereoregular polyesters with controlled molecular weights and well‐defined chain ends were achieved. The effects of stereoconfiguration and substituent on polymerization kinetics and thermodynamics as well as the thermal properties of resultant polyesters were investigated. Of note, the stereoregular polyesters are semi‐crystalline materials with melting temperatures up to 176 °C, even higher than the commodity polyolefin plastics. These polyesters can be depolymerized back to recover pristine monomers, thus successfully establishing a closed‐loop life cycle. [ABSTRACT FROM AUTHOR]

The low temperature condition, long reaction time and associated high energy inputs involved in the polymerization process still hampered the scalable production of poly(γ‐butyrolactone) (PγBL) via ring‐opening polymerization (ROP) of low strained γBL due to its unfavorable thermodynamics. In this contribution, we presented the rapid ROP of γBL using a bisurea in combination with an organophosphazene base as the binary catalyst. Well‐defined PγBL samples with various terminal groups were prepared by using different alcohol initiators. The bisurea as a co‐catalyst exhibited much higher catalytic activity even compared to the most active monourea in previous report as supported by the kinetic experiments. A moderate monomer conversion of 61% was achieved within 10 mins, producing high‐molecular‐weight PγBL with Mn up to 37.5 kDa and good mechanical properties. The short polymerization time considerably reduced the energy cost for the ROP of γBL conducted at low temperature condition. This study may clear away obstacles for the scalable production and practical applications for PγBL. [ABSTRACT FROM AUTHOR]

It is greatly desirable to develop degradable polymers from easily accessible chemicals. In addition to well‐known degradable aliphatic polyesters, poly(ether‐ester) prepared from 1, 4‐dioxan‐2‐one with perfectly alternative ether and ester bonds is a new type of degradable polymer. Due to the low strain of six‐membered 1, 4‐dioxan‐2‐one ring, it remains a challenge to realize the effective and controllable ring‐opening polymerization (ROP) of 1, 4‐dioxan‐2‐one derived monomers despite several catalysts have been attempted. In recent years, the combination of organobase/(thio)urea binary catalytic system has displayed great activity and versatility in the ROP of cyclic esters. Herein, we studied the ROP of 3‐methyl‐1, 4‐dioxan‐2‐one (MDO) using the combinations of various organobases and ureas as catalysts at relatively low temperature. We found that 1, 8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU)/urea pair showed great overall performance in the ROP of MDO, achieving monomer conversion up to 82% within 7 h at −40 °C. Notably, DBU/urea binary catalytic system achieved higher catalytic activity as well as better control over molecular weights and molecular weight distributions compared to previously reported catalysts. The obtained PMDO can completely depolymerize to recover MDO monomer by simple thermolysis, thus established a close‐loop life cycle. [ABSTRACT FROM AUTHOR]

It is a highly attractive strategy to develop chemically recyclable polymers to establish a circular plastic economy. Despite the recent advancements, chemically recyclable polymers still face challenges including high energy cost for polymer preparation or recycling, poor monomer recovery selectivity and efficiency as well as undesired material performance. In this contribution, we present the chemoselective controlled ring‐opening polymerization of bio‐renewable bifunctional α‐methylene‐δ‐valerolactone (MVL) to produce exclusive functionalizable polyester using strong base/urea binary catalysts. The obtained polyester with high molar mass exhibits good tensile strength comparable to that of some commodity plastics. Remarkably, the obtained polyester can be depolymerized to recover pristine monomer with a 96 % yield by thermolysis, thus successfully establishing a closed‐loop life cycle. [ABSTRACT FROM AUTHOR]

The development of chemically recyclable polymers presents the most appealing solution to address the plastics' end‐of‐use problem. Despite the recent advancements, it is highly desirable to develop chemically recyclable polymers from commercially available monomers to avoid the costly and time‐consuming commercialization. In this contribution, we achieve the controlled ring‐opening polymerization (ROP) of bio‐sourced δ‐caprolactone (δCL) using strong base/urea binary catalysts. The obtained PδCL is capable of chemical recycling to δCL in an almost quantitative yield by thermolysis. Sequential ROP of δCL and l‐lactide (l‐LA) affords well‐defined PLLA‐b‐PδCL‐b‐PLLA triblock copolymers, which behave as thermoplastic elastomers with excellent elastic recovery, tensile strength and ultimate elongation. The upcycling of PLLA‐b‐PδCL‐b‐PLLA to recover ethyl lactate and δCL with high yields is achieved by refluxing with ethanol and then distillation under reduced pressure. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: Substantial progresses have been made toward the development of metal‐free catalysts for stereoselective ring‐opening polymerization (ROP) of rac‐lactide. Yet the discovery of organic catalysts effective at ambient temperature remains a major challenge. Here, the bifunctional H‐bonding catalyst SQ‐1 containing a basic tertiary amine and squaramide motif proved to be good candidate for the stereoselective ROP of rac‐lactide at room temperature, yielding stereoregular polylactide with controlled molecular weights (up to 21.1 kg/mol) and high tacticity (PiESC up to 0.88). Furthermore, binary H‐bonding catalytic system consisting of squaramides (SQ‐2 to SQ‐6) and 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) could efficiently promote the ROP of rac‐lactide at room temperature within short reaction time. Among them, the most bulky squaramide SQ‐2 exhibited the best steroselectivity towards the ROP of rac‐lactide without transesterification side reactions during the polymerization process. The resulting polylactides were proved to have controlled molecular weights as high as 22.2 kg/mol and narrow distributions (1.10—1.24). [ABSTRACT FROM AUTHOR]

Comprehensive Summary Copolymerization as an efficient strategy can provide an opportunity to create new closed‐loop recyclable polymeric materials with tailored properties that are generally inaccessible to the individual homopolymers. In this contribution, the bulk ring‐opening copolymerization of bio‐renewable δ‐caprolactone and trans‐hexahydro‐(4,5)‐benzofuranone was achieved to produce closed‐loop recyclable copolyesters by using an organobase/urea binary catalyst at room temperature. The obtained copolyesters exhibited composition‐dependent thermal properties. Remarkably, the obtained copolyesters were able to depolymerize back to recover the corresponding monomers under mild conditions. The copolyesters with suitable compositions can be directly used as pressure‐sensitive adhesives (PSAs) that possessed comparable peel strength with the commercially available PSA scotch tapes. When the copolyesters were mixed with plasticizers, the as‐prepared PSAs exhibited desirable adhesive failure and can be used as removable post‐it note. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: Substantial progresses have been made toward the development of metal‐free catalysts for stereoselective ring‐opening polymerization (ROP) of rac‐lactide. Yet the discovery of organic catalysts effective at ambient temperature remains a major challenge. Here, the bifunctional H‐bonding catalyst SQ‐1 containing a basic tertiary amine and squaramide motif proved to be good candidate for the stereoselective ROP of rac‐lactide at room temperature, yielding stereoregular polylactide with controlled molecular weights (up to 21.1 kg/mol) and high tacticity (PiESC up to 0.88). Furthermore, binary H‐bonding catalytic system consisting of squaramides (SQ‐2 to SQ‐6) and 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) could efficiently promote the ROP of rac‐lactide at room temperature within short reaction time. Among them, the most bulky squaramide SQ‐2 exhibited the best steroselectivity towards the ROP of rac‐lactide without transesterification side reactions during the polymerization process. The resulting polylactides were proved to have controlled molecular weights as high as 22.2 kg/mol and narrow distributions (1.10—1.24). [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]

Tough and transparent poly(L-lactic acid)/poly(D-lactide)-b-poly(butadiene)-b-poly(D-lactide) (PLLA/PDLA-PB-PDLA) film with balanced strength was obtained. The PDLA-PB-PDLA triblock copolymer was firstly synthesized by ring-opening polymerization (ROP) of D-lactide using bihydroyl-terminated polybutadiene as macroinitiator, and then the obtained triblock copolymer was mixed with PLLA in solution. The blended films kept in good transparence even when the loading of PDLA-PB-PDLA reached to 15 wt%. Meanwhile, the elongation at break of the PLLA/PDLA-PB-PDLA film increased by ∼10 times without a significant reduction in tensile strength as compared with that of pure PLLA. The mechanical property was ascribed to the synergetic effect of the flexible PB chains and the stereocomplex crystals formed between PLLA matrix and PDLA chains. "Salami-like" dispersed-phase with nanometer scales was observed, which would contribute to the transparency of the blended film. The tensile fractured morphologies indicated that shear yield of the matrix and cavitation might be the major toughening mechanism of PLLA/PDLA-PB-PDLA film. We prepared tough and transparent poly(L-lactic acid) film with balanced tensile strength by blending with poly(D-lactide)-b-poly(butadiene)-b-poly(D-lactide) triblock copolymer. [Display omitted] • Tough and transparent poly(L-lactic acid)/poly(D-lactide)-b-poly(butadiene)-b-poly(D-lactide) film with balanced strength. • The mechanical properties were ascribed to the synergetic effect of the flexible PB chains and the stereocomplex crystals. • "Salami-like" dispersed-phase with nanometer scales would contribute to the transparency of the blended film. • Shear yield of the matrix and cavitation might be the major toughening mechanism of PLLA/PDLA-PB-PDLA film. [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]