Ring-Opening Copolymerization of Cyclohexene Oxide and Cyclic Anhydrides Catalyzed by Bimetallic Scorpionate Zinc Catalysts.

Felipe De La Cruz-Martínez,Agustín Lara-Sánchez,Luis F Sánchez-Barba,Andrés Garcés,Carlos Alonso-Moreno,Marc Martínez De Sarasa Buchaca,Juan Fernández-Baeza,José A Castro-Osma,Almudena Del Campo-Balguerías

doi:10.3390/polym13101651

Felipe De La Cruz-Martínez, Agustín Lara-Sánchez + Show 7 more

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https://doi.org/10.3390/polym13101651

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Abstract

The catalytic activity and high selectivity reported by bimetallic heteroscorpionate acetate zinc complexes in ring-opening copolymerization (ROCOP) reactions involving CO2 as substrate encouraged us to expand their use as catalysts for ROCOP of cyclohexene oxide (CHO) and cyclic anhydrides. Among the catalysts tested for the ROCOP of CHO and phthalic anhydride at different reaction conditions, the most active catalytic system was the combination of complex 3 with bis(triphenylphosphine)iminium as cocatalyst in toluene at 80 °C. Once the optimal catalytic system was determined, the scope in terms of other cyclic anhydrides was broadened. The catalytic system was capable of copolymerizing selectively and efficiently CHO with phthalic, maleic, succinic and naphthalic anhydrides to afford the corresponding polyester materials. The polyesters obtained were characterized by spectroscopic, spectrometric, and calorimetric techniques. Finally, the reaction mechanism of the catalytic system was proposed based on stoichiometric reactions.

Highlights

Commercial polyester materials are currently produced by polycondensation reactions between diols and diacids at high reaction temperature and prolonged reaction times to afford high-molecular weight polyesters [1,2]
The ring-opening copolymerization (ROCOP) reaction of epoxides and cyclic anhydrides requires the use of a catalyst system, which is usually comprised by a combination of a metal complex and a nucleophile source [15]
Encouraged by the catalytic activity and selectivity displayed by these complexes in ROCOP reactions involving CO2, in this work, we have studied the use of these friendly zinc complexes as catalysts for the ROCOP of cyclohexene oxide (CHO) and cyclic anhydrides with the aim of extend the substrate scope for these complexes in the synthesis of polymeric materials

Summary

Introduction

Commercial polyester materials are currently produced by polycondensation reactions between diols and diacids at high reaction temperature and prolonged reaction times to afford high-molecular weight polyesters [1,2]. A broad range of biodegradable polyesters have been obtained via ring-opening polymerization (ROP) of cyclic esters (Scheme 1a) as a more sustainable alternative to traditional polyester materials [3,4,5,6,7,8,9,10]. The microstructure and properties of the resulting polymers are restricted by the limited number of commercially available cyclic esters In this regard, the ring-opening copolymerization (ROCOP) of epoxides and cyclic anhydrides (Scheme 1b) has emerged in recent years as alternative to the ROP of cyclic esters to prepare a larger number of polyester materials with a broader range of microstructures, properties and applications [15]. A wide range of metal complexes, including chromium [16,17,18,19,20], magnesium [21,22,23],

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