Synthesis and Catalytic Activity of Gallium Schiff‐base Complexes in the Ring‐Opening Homo‐ and Copolymerization of Cyclic Esters

Abstract

Tetranuclear Ga(III) complexes L1–32Ga4(t‐Bu)8 1–3 are synthesized and characterized (elemental analysis, IR, 1H, 13C, DOSY NMR spectroscopy, XRD) and their activity in the ring‐opening polymerization (ROP) of lactide (LA) and ϵ‐caprolactone (ϵ‐CL) is reported. Complex 1 is the most active homopolymerization catalyst in the presence of benzyl alcohol (BnOH), yielding isotactic‐enriched polylactides (PLAs) with Pm (probably of mesomerism) values up to 0.72 by a first order kinetic with respect to the monomer concentration. The living character of the polymerization process was confirmed by a polymerization resumption experiment. Complexes 1–3 are also active catalysts in the copolymerization of LA and ϵ‐CL, and sequential addition of both monomers gave well‐defined block copolymers with narrow Đ values (distributions of molecular weight).

Crafting sustainable solutions: architecting biodegradable copolymers through controlled ring-opening copolymerization

“…27). 90 l -LA was added after ε-CL was polymerized at 100 °C in toluene ([ε-CL] : [ l -LA] : [cat] : [BnOH] = 300 : 300 : 1 : 4). The M n values of the copolymers were observed to increase as the second block grew, as predicted by the GPC studies, which revealed a monomodal peak and narrow PDI values.…”

Dinuclear Mg Complex-Mediated Ring-Opening Polymerization of Lactones: High Molecular Weight and Enhanced Performance

“…For the anionic ROP of ε-CL, effective catalysts are vital for efficiently synthesizing high-performance PCLs. A series of metal complexes, including aluminum (Al III )-, magnesium (Mg II )-, calcium (Ca II )-, and zinc (Zn II )-based complexes, have been developed for this ROP. − The ROP of ε-CL can proceed efficiently, providing PCLs with controlled MWs and narrow distributions. For example, PCL with an M n of 138 kg/mol using the mononuclear Mg complex with an ε-CL/Mg complex feed ratio of 1600/1 was achieved by Zhang et al In addition, binary organocatalyst systems comprising organic bases and benzyl alcohol (BnOH) have been demonstrated to be effective in the transformation of ε-CL into PCL .…”

Group 13 salphen compounds (In, Ga and Al): a comparison of their structural features and activities as catalysts for cyclic carbonate synthesis

“…Meanwhile, Ga and In complexes bearing Schiff-base ligands have previously been applied as catalysts for the ringopening polymerization (ROP) of lactide, highlighting their potential in Lewis acid catalysis. [8][9][10][11][12][13][14] Specifically related to the work in this study, in 2018, Williams and co-workers described the application of [InCl(salphen)] complexes and derivatives for the co-polymerization of epoxides and CO 2 to efficiently form polycarbonates. 15 More recently, Mehrkhodavandi and co-workers have also developed active In-based catalysts for this conversion.…”