Kinetic Studies of the Alternating Copolymerization of Cyclic Acid Anhydrides and Epoxides, and the Terpolymerization of Cyclic Acid Anhydrides, Epoxides, and CO₂ Catalyzed by (salen)Cr^IIICl

Abstract

Copolymerization of a series of cyclic acid anhydrides with several epoxides using (salen)CrCl/onium salt catalysts has afforded polyesters with high molecular weights and narrow molecular weight distributions. The (salen)CrCl catalyst in the presence of the onium salts with formula PPNX (X = Cl–, N3 –) for the copolymerization of the anhydrides, maleic (MA), succinic (SA), phthalic (PA), cyclohexene (CHE), and cyclohexane (CHA) with the epoxides, cyclohexene oxide (CHO), propylene oxide (PO), and styrene oxide (SO) resulted in completely alternating enchainment of monomers to provide pure polyesters. Temperature dependent studies of the ring-opening copolymerization of phthalic anhydride and cyclohexene oxide monomers in toluene solution have yielded activation parameters of ΔH ‡ = 67.5 kJ mol–1 and ΔS ‡ = −95.3 J mol–1, where the rate limiting step was ring-opening of the epoxide by the enchained anhydride. For the cyclic acid anhydride (CHA), the relative order of reactivity with epoxides decreased PO > CHO ≥ SO, and for the epoxide (CHO) the relative rate of copolymerization was CHA > PA > CHE. The (salen)CrCl/PPNN3 catalyst system was also shown to effectively terpolymerize CHO/phthalic anhydride/CO2 to afford diblock copolymers, thereby producing in a one pot synthesis poly(ester-co-carbonate). T g values of the synthesized polyesters displayed a temperature range over 130 °C, from +95 °C to −39 °C.

Ring-opening copolymerization (ROCOP): synthesis and properties of polyesters and polycarbonates

“…21 They found that 6b on its own is inactive for CHO-PA copolymerization. Using 6b, PPN + X À (X = Cl À , N 3 À , DNP À ) salts were slightly better co-catalysts than NBu 4 + X À (X = Br À , I À ) salts.…”

Microwave-Assisted Catalytic Synthesis of Bio-Based Copolymers from Waste Cooking Oil

“…Alternating copolymerization of various epoxides and cyclic anhydrides with (salen)CrCl/onium salt as catalysts also yield polyesters with high molecular weights and narrow distribution values [20]. Among metal complexes, the chromium salen complex has proved to be the most effective catalyst for copolymerization of epoxides such as cyclohexene oxide, propylene oxide, styrene oxide, limonene oxide and anhydrides (succinic, maleic and phthalic anhydrides) [20][21][22].…”

Alternating copolymerization of CHO and MA catalyzed by the hetero-bimetallic Zn-Yb-Salen complex

“…Since the precedent milestone on the catalytic coupling of propylene oxide (PPO) and MA [6], the copolymerized epoxide monomers are extended to aromatic epoxides [7], and the catalyst systems are proceeded from unstable metal alkoxides [8] to stable porphyrinato- [9], Salenbased [10] or asymmetric Salen-analogous M(III) complexes [11]. In this context, from the viewpoint of "green" synthesis, the bulk solvent-free copolymerization procedure, together with the development of low toxicity catalysts are much deserved.…”

“…On the other hand, it remains a real challenge [12] to realize the perfectly alternating copolymerization from epoxide and MA with a quantitative control. Based on the effectiveness of ring-opening copolymerization of CHO and MA using Zn(II) [13] or M(III)-Salen complexes [10] as catalysts, it is of particular interest on the catalytic behaviors from their Zn(II)-Ln(III) catalytic system with two active species while relatively lower toxicity.…”

“…Further based on their characterization analysis, a strong absorption at 1094 cm −1 attributed to the ν as (\ \C\ \O\ \C) vibration of ether in FT-IR, together with the proton resonance (δ = 3.37 ppm) assigned to the ether-character\ \O\ \CH group in 1 H NMR (Fig. 2) renders the polymers characteristic of high ether-content (57-61%) poly(ester-coether)s. Noticeably, the copolymerization of CHO and MA proceeds smoothly in the presence of the catalyst 1 alone (entry 2) is incomparable of the fact of much lower activities from porphyrinato- [9] or Salenbased M(III) complex [10] alone, which should be resulted from the selfowned normal OAc − initiators around the two active species in the catalyst 1. Nonetheless, the stronger coordination inserting ability of CHO than that of MA endows the preferred initiation of ring-opening of CHO by OAc − anions [6], leading to the formation of highly ether-linked poly(ester-co-ether)s. However, through the involvement of a nucleophilicity cocatalyst DMAP, the reversible while strong catalyst-cocatalyst interactions can further promote the activation of the catalytic species [19].…”