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Polyester and polyether are two key oxygenated polymers, and completely alternative sequence of poly(ester-alt-ether) could efficiently combine the advantages (including flexibility, degradability, etc.) of both segments. Currently, despite their copolymers could be synthesized from one-pot mixture of cyclic esters and epoxides, perfectly alternative microstructure is very challenging to realize and typically restricted to certain monomer pairs. Moving forward, synthesizing poly(ester-alt-ether) from commercially available and largescale monomers would be a significant advance. For example, successfully commercialized poly(glycolic acid) (PGA), which is not easily soluble in polymers due to its high crystallinity and is brittle and difficult to control the degradation cycle, would encounter a new paradigm if engineered into poly(ester-alt-ether). In this work, starting from the design of monomer with hybrid structures, we successfully synthesized a series of 1,4-dioxan-2-one containing different substituents based on glycolide (GA) and epoxides using commercially available Salen-Cr(III) and PPNCl catalytic systems. The new monomers underwent ring-opening polymerization (ROP) to form a series of poly(ester-alt-ether) with perfectly alternating glycolic acid and propylene glycol repeat units under catalytic system of thiourea/base. The poly(ester-alt-ether) have significantly lower glass-transition temperature than PGA. Additionally, the poly(ester-alt-ether) can be chemically recovered to monomer using Sn(Oct)2 or 1,8-diazabicyclo[5.4.0]undecane-7-ene (DBU) as a catalyst in solution, thus establishing a closed-loop life cycle. From monomers derived from GA and epoxides, this work furnishes a novel strategy for the synthesis of poly(ester-alt-ether) with chemical recyclability. [ABSTRACT FROM AUTHOR]

As a representative class of sustainable polymer materials, biodegradable polymers have attracted increasing interest in recent years. Despite significant advance of related polymerization techniques, realizing high sequence‐control and easy‐handling in ring‐opening (co)polymerizations still remains a central challenge. To this end, a promising solution is the development of valence‐variable metal‐based catalysts for redox‐induced switchable polymerization of cyclic esters, cyclic ethers, epoxides, and CO2. Through a valence‐determined electron effect, the switch between different catalytically active states as well as dormant state contributes to convenient formation of polymer products with desired microstructures and various practical performances. This redox‐controlled switchable strategy for controlled synthesis of polymers is overviewed in this Review with a focus on potential applications and challenges for further studies. [ABSTRACT FROM AUTHOR]

With the global demand for sustainable development, there has been an increasing interest in using natural biomass as raw resources to produce sustainable polymers as an alternative to petroleum‐based polymers. Because monocomponent biodegradable polymers are often insufficient in performance, copolymers with well‐engineered block structures are synthesized to reach wide tunability. Switchable polymerization is such a practical strategy to produce biodegradable block copolymers with diverse performance. This review focus on the performance of block copolymers bearing biodegradable polymer segments produced by diverse switchable polymerization. We highlight two main segments that are critical for biodegradable block copolymers, i. e. polyester and polycarbonate, summarize the multiple characters of materials from switchable polymerization such as antibacterial, shape memory, adhesives, etc. The state‐of‐the‐art research on biodegradable block copolymers, as well as an outlook on the preparation and application of novel materials, are presented. [ABSTRACT FROM AUTHOR]

Electrochemical redox‐control is an emerging strategy for the regulation of polymerization process without the addition of external oxidants and reductants, which enables the control over composition, microstructure and properties of the polymer products. In this paper, based on the chemical selectivity of heterometallic Salen‐Co‐Mn complexes of different valences, an electrochemically switchable strategy was developed for the copolymerization of lactide (LA), CO2 and epoxides. The switchable redox reactions endowed this system with the capability to easily synthesize a multi‐block copolymer of polylactide (PLA) and polycarbonate (PC). Moreover, the multi‐block copolymer could be further modified by introducing various monomers with different microstructures and functional groups. [ABSTRACT FROM AUTHOR]

Using adamantane-1,3-diamine and 3,5-di-tert-butylsalicylic aldehyde as raw materials, the generated salen aluminum complex was characterized by 1H, 13C NMR spectroscopy and elemental analysis. After isopropyl alcohol activation treatment, the complex has good activity (70.3-95.6%), which can provide poly(D,L-lactide) with a Pm of 0.87 for rac-lactide. [ABSTRACT FROM AUTHOR]

Switchable polymerization is an attractive strategy to enable the sequential selectivity of multi‐block polyesters. Besides, these well‐defined multi‐block polyesters could enable further modification for wider applications. Herein, based on the reversible insertion of CO2 by Salen‐MnIII, a new monomer controlled self‐switchable polymerization route was developed. Chemoselective ring opening copolymerization of O‐carboxyanhydrides (OCAs) and lactide (LA) was explored without cocatalyst. The sequential conversion of OCAs and LA into the polymer chain could form multi‐block polyesters. Based on this strategy, a series of multi‐block polyesters with different pendant groups were synthesized. Furthermore, by modifying the propargyl‐containing copolymers with quaternary ammonium groups, we have realized antibacterial functionalization of PLA. These results imply the potential application of this strategy for the fabrication of functional polymers for biomedical applications. [ABSTRACT FROM AUTHOR]

A series of zinc silylamido complexes based upon NNO tridentate enolic Schiff base framework have been synthesized and characterized. These complexes were tested for the ring opening polymerization of lactide and ε-caprolactone, exhibiting notably high activity at ambient temperature. The influence of imine bridge length and substituents of diketone over the course of polymerization was investigated in details. Remarkably, 4a was confirmed to be a rare example of exceedingly active and robust zinc catalysts, achieving major transformation of lactide under extremely low loading (0.025 mol%) within 18 min. The influence of various monomers as well as the polymerization mechanism have also been discussed. [ABSTRACT FROM AUTHOR]

A dinuclear Salph-Al complex/bis(triphenylphosphine)iminium chloride catalyst system was synthesized and employed for cyclohexene oxide (CHO) and CO2 copolymerization. The catalyst system had an excellent selectivity of 99 % for carbonate linkages and the resultant poly(cyclohexene carbonate) (PCHC) had a high glass transition temperature ( Tg) of 123.8 °C and a thermal decomposition temperature (5 % weight loss; Td 5 %) of 265 °C. Furthermore, this catalyst system was active in the polymerization of phthalic anhydride (PA) and epoxides. Poly(CHO- alt-PA) was completely alternating, and had improved thermal properties ( Tg=142.7 and Td 5 %=295 °C) compared with PCHC. The Tg values of the polyesters could be adjusted by addition of PO to the CHO/PA reaction system. For the CHO/PO/PA terpolymerization, CHO and PO participated concurrently and proportionally in the chain growth and the obtained terpolyesters had tunable Tg values from 62.8 to 142.7 °C depending on the CHO/PO feed ratio. [ABSTRACT FROM AUTHOR]

ABSTRACT A series of bimetallic aluminum Schiff-base complexes have been prepared and characterized. The complexes used as catalysts were applied in the lactide polymerization to test their activities and stereoselectivities. All polymerizations are living, as evidenced by the narrow polydispersities and the good fit between calculated and found number-average molecular weights of the isolated polymers. Isotactic enriched polylactide was obtained by using these complexes. Kinetic studies indicated that the polymerizations are both first-ordered with respect to lactide monomer and catalyst. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1344-1352 [ABSTRACT FROM AUTHOR]

A series of zinc complexes based on asymmetrical N,N,O-tridentate ligands were prepared via binaphthyl diamine derivatives. These complexes were characterized and employed as catalysts in lactide polymerization. The X-ray diffraction analyses revealed that molecular structures of 1b and 2b were mononuclear complexes with zinc atoms in distorted octahedral geometries. Upon co-catalysis with isopropanol, complex 2a showed the highest activity among these zinc complexes for the ring-opening polymerization of l-lactide, and complex 3a exhibited the highest stereoselectivity for the ring-opening polymerization of rac-lactide affording substantially isotactic polylactide (PLA) with a Pm of 0.62. The polymerization kinetics using 2a as a catalyst was studied in detail. The kinetics of the polymerization results revealed that the rates of polymerization were first-order both in the monomer and the catalyst, and there was a linear relationship between the l-LA conversion and the number-average molecular weight of PLA with a narrow molecular distribution (1.07–1.17). The activation energy (31.49 kJ mol−1) was deduced according to the Arrhenius equation. [ABSTRACT FROM AUTHOR]

A new radical-Lewis acid system has been discovered to achieve the ring-opening polymerization of tetrahydrofuran. Different types of reaction mechanisms were discovered for the initiation and polymerization processes. The proposed initiation mechanism was studied by MALDI-TOF and ESI-MS as a radical substitution mechanism and polymerization was a coordination-insertion mechanism. And polytetrahydrofuran with high molecular weight (M n = 14.6 × 104 g mol−1) and narrow molecular weight distribution (PDI = 1.44) could be obtained. ◆new method for the ring-opening polymerization of tetrahydrofuran◆metal free◆radical-Lewis acid system◆new radical initiation. [Display omitted] • Ring opening of THF successfully proceeds via radical substitution reaction. • A variety of radical initiators can initiate the ring-opening polymerization of THF. • The initiation of the system is a radical substitution mechanism and the polymerization is a coordination-insertion mechanism. • A new method for obtaining high molecular weight PTHF is offered. [ABSTRACT FROM AUTHOR]