Alternating copolymerization of carbon dioxide and epoxide catalyzed by an aluminum Schiff base–ammonium salt system

Abstract

The alternating copolymerization of carbon dioxide (CO2) and cyclohexene oxide (CHO) with an aluminum Schiff base complex in conjunction with an appropriate additive as a novel initiator is demonstrated. A typical example is the copolymerization of CO2 and CHO with the (Salophen)AlMe (1a)–tetraethylammonium acetate (Et4NOAc) system. When a mixture of the 1a–Et4NOAc system and CHO was pressurized by CO2 (50 atm) at 80 °C in CH2Cl2, the copolymerization of CO2 and CHO took place smoothly and produced a high polymer yield in 24 h. From the IR and NMR spectra, the product was characterized to be a copolymer of CO2 and CHO with an almost perfect alternating structure. The matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry analysis indicated that an unfavorable reaction between Et4NOAc and CH2Cl2 and a possible chain‐transfer reaction with concomitant water occurred, and this resulted in the bimodal distribution of the obtained copolymer. With carefully predried reagents and apparatus, the alternating copolymerization in toluene gave a copolymer with a unimodal and narrower molecular weight distribution. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4172–4186, 2005

Alternating copolymerization of CO2 with propylene oxide and terpolymerization with aliphatic epoxides by bifunctional cobalt Salen complex

“…A similar solvent effect was reported for copolymerization with binary catalyst systems. 12,20,30 The Mn value of the copolymer obtained increased linearly in proportion to the PO conversion, retaining a narrow but bimodal distribution (Figure 2). The Mn values were much lower than the theoretical values because of chain transfer caused by trace quantities of water in the copolymerization system.…”

“…Similar results have been reported before. 12,20 To obtain copolymers with higher Mn values, copolymerization was attempted at a higher PO/complex 1 ratio of 6000. With a reaction time up to 50 h, the molecular weight reached 108.6 kg mol À1 , and the selectivity for PPC formation did not show an observable decrease (PPC/PC¼97; entry 5).…”

“…After the pioneering work by Inoue and co-workers 5,6 in the late 1960s, a wide variety of metal catalysts were developed for this transformation. [7][8][9][10][11][12][13][14][15][16][17][18] Among the metal complex catalysts, Co Schiff base complexes are effective catalysts for CO 2 / epoxides coupling reactions, 11,13,[15][16][17] because these complexes can control the molecular weights and distribution of the polycarbonates produced and regulate the selective formation of alternating copolymers. However, Co Schiff base complexes are not highly active at a high monomer/catalyst mole ratio in conjunction with a Lewis base or organic salt, which prevents them from becoming commercially viable.…”

Ionic Liquids in Green Carbonate Synthesis

“…The immobilized ILs could be reused up to four consecutive runs without considerable loss of activity and f(CO 2 ). Several research groups reported that various ILs could be effective cocatalysts in the copolymerization of CO 2 and epoxides with metal salen or metal porphyrin complexes [126][127][128][129][130]. In some cases, it was shown that the activities of theses metal complexes were drastically enhanced by the co-presence of IL, although they had no or a very low activity for the coplymerization in the absence of IL.…”

“…They also achieved the synthesis of block copolymers. The same group also used the system of Al salen complex and [Et 4 N]OAc for the copolymerization of CO 2 and CHO [127]. This catalyst system required a higher reaction temperature of 80°C to obtain the copolymer with a high yield and high f(CO 2 ), compared to the above mentioned catalyst system using Al porphyrin complex.…”