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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]

Degradable polyester elastomers are highly desirable for biomedical applications. Here, highly transparent and degradable aliphatic polyester elastomers were prepared using the ring‐opening copolymerization (ROCP) of commercial monomers, followed by a photo‐crosslinking process. A series of the semi‐crystalline copolyester (PMBL‐co‐PBL‐co‐PCL) precursors with different molecular weights and pendent vinyl contents were synthesized by one‐pot ROCP of α‐methylene‐γ‐butyrolactone (MBL), ε‐caprolactone (ε‐CL) and γ‐butyrolactone (γ‐BL). Then, UV irradiation was applied to photo‐crosslink the precursors to obtain several elastomers. The obtained aliphatic polyester elastomers (CPEs) displayed excellent mechanical properties with high tensile strength (11.3 MPa), high elongation at break (1300%) and high elastic recovery (about 99% after 10 hysteresis cycles). In addition, the elastomer showed much better stability than uncrosslinked (co)polyesters, but maintained degradability in the basic aqueous solution, with ~30% of the mass loss in 1 M NaOH solution after 30 days. Through efficient ROCP, we demonstrated a strategy to prepare degradable CPEs bearing high strength, good elasticity, excellent resilience and degradation capability, which can serve as sustainable elastomers for various applications. [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]

Comprehensive Summary: A series of titanium amido complexes (1‐Ti(NMe2)2 to 4‐Ti(NMe2)2) bearing NNO‐tridentate ligands was synthesized from the reactions of phenoxy‐imine‐amine ligands with one equivalent of Ti(NMe2)4. Subsequently, titanium dichloride complexes (1‐TiCl2 to 4‐TiCl2) were prepared by treatment of titanium amido complexes with excess Me3SiCl in toluene. All metal complexes were characterized by 1H and 13C NMR spectroscopy, and the molecular structures of complexes of 2‐Ti(NMe2)2, 2‐TiCl2, and 4‐TiCl2 in the solid state were determined by single‐crystal X‐ray diffraction. Upon activation with MAO, titanium dichloride complexes as single‐site catalysts were extremely active toward ethylene homopolymerization with great control on molecular weight and distribution. In particular, 3‐TiCl2/MAO exhibited an activity as high as 1.35 × 108 g(PE)·mol−1(Ti)·h−1 at 70°C and produced polyethylene with high molecular weight (41.7 × 104 g∙mol−1) and very narrow distribution (Đ = 1.23). In the presence of 1‐octene as comonomer, linear low‐density polyethylenes (LLDPEs) with ultrahigh molecular weights (Mw = 136—326 × 104 g∙mol−1) and narrow distributions (Đ = 1.20—1.50) were successfully synthesized. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: A series of titanium amido complexes (1‐Ti(NMe2)2 to 4‐Ti(NMe2)2) bearing NNO‐tridentate ligands was synthesized from the reactions of phenoxy‐imine‐amine ligands with one equivalent of Ti(NMe2)4. Subsequently, titanium dichloride complexes (1‐TiCl2 to 4‐TiCl2) were prepared by treatment of titanium amido complexes with excess Me3SiCl in toluene. All metal complexes were characterized by 1H and 13C NMR spectroscopy, and the molecular structures of complexes of 2‐Ti(NMe2)2, 2‐TiCl2, and 4‐TiCl2 in the solid state were determined by single‐crystal X‐ray diffraction. Upon activation with MAO, titanium dichloride complexes as single‐site catalysts were extremely active toward ethylene homopolymerization with great control on molecular weight and distribution. In particular, 3‐TiCl2/MAO exhibited an activity as high as 1.35 × 108 g(PE)·mol−1(Ti)·h−1 at 70°C and produced polyethylene with high molecular weight (41.7 × 104 g∙mol−1) and very narrow distribution (Đ = 1.23). In the presence of 1‐octene as comonomer, linear low‐density polyethylenes (LLDPEs) with ultrahigh molecular weights (Mw = 136—326 × 104 g∙mol−1) and narrow distributions (Đ = 1.20—1.50) were successfully synthesized. [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]

The properties and applications of silicone elastomers depended on the molecular structure and composition of polysiloxane precursors, which were the most technologically important silicon-based polymers. Preparation of perfect diphenyl silicone elastomers was challenging due to the unexpected branches formed during the ring-opening copolymerization (ROCP) of phenylcyclosiloxane monomer. In this contribution, diphenyl silicone elastomer precursors with controlled structure were successfully prepared by cyclic trimeric phosphazene base (CTPB) catalyzed ROCP of octamethylcyclotetrasiloxane (D 4), octaphenylcyclotetrasiloxane (D 4 8Ph), and 2,4,6,8-tetravinyl-2,4,6,8-tetramethylcyclotetrasiloxane (D 4 Vi) with high molecular weight up to 551.0 kg/mol and dispersity (Đ) ≤ 2.50. 29Si NMR characterization verified the random microstructures of the resulting diphenyl containing polysiloxanes without chain branching. Moreover, the silica-filled elastomer prepared from poly(dimethylsiloxane- co -vinylmethylsiloxane) (PMVS) and poly(dimethylsiloxane- co -diphenylsiloxane- co -vinylmethylsiloxane) (PMPVS) precursors exhibited very high elasticity, which can be stretched to 1043% with a high tensile strength of 7.7 MPa. Thermal oxidation aging test proved the excellent thermal aging resistance of the phenyl-containing silicone elastomers. This work demonstrated facile method to prepare high quality diphenyl containing polysiloxane precursor toward robust silicone elastomers. [Display omitted] • Diphenyl silicone elastomer precursors with controlled structure were successfully prepared by CTPB catalyzed ROCP. • Silica-filled elastomer prepared from PMVS and PMPVS precursors exhibited very high elasticity. • Thermal oxidation aging test proved the excellent thermal aging resistance of the phenyl-containing silicone elastomers. [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]