ppm-Level Thermally Switchable Yttrium Phenoxide Catalysts for Moisture-Insensitive and Controllably Immortal Polymerization of rac-Lactide

Abstract

Exploring the moisture-insensitive catalysis system for the ring-opening polymerization of cyclic esters is very valuable for the synthesis of polyesters in industry. To reduce metal residue in final polymers, using ppm-level catalysts for the moisture-insensitive and controllable ROP system is still a big challenge until now. In this work, as a general strategy, a series of D 3 symmetrical binuclear yttrium phenoxides were applied in the moisture-insensitive ringopening polymerization of rac-lactide. The structures of these yttrium complexes can be reversibly switched between highly active and less active species in the presence of water via changing temperature. These catalysts are so robust in air, the loading of catalyst can be as low as 15 ppm, and one molecular catalyst can mediate the synthesis of more than 1000 polymer chains. The low initiation efficiency of water was proved unambiguously; hence, the polymerizations are controllable with a highly efficient initiator of alcohol in moisture condition, and the high molecular weight of polylactide can reach 78.0 kg/mol. What is more, this moisture-insensitive system can show some heteroselectivity in the ROP of rac-lactide.

Weak Lewis Pairs as Catalysts for Highly Isoselective Ring-Opening Polymerization of Epimerically Labile rac-O-Carboxyanhydride of Mandelic Acid

“…Thus, a subtle balance of Lewis acid of metal ion has to be found. To reduce this negative effect and after many trials (the unsuccessful examples include Salen-Al-OR, 54 (BDI)Zn-OR, 19 yttrium phenolate complexes, 55,56 and so on), aminobisphenolate zinc complexes were found to be good candidates (Figure 1C), which have been utilized for the polymerization of εcaprolactone by Hillmyer, Tolman, and co-workers. 57 As our design, using aminobisphenolate zinc complex 1 as a Lewis acid, 3-F-Py as a Lewis base, and L-methyl lactate (L-ML) as an initiator with a 1:1:1 mole ratio of [Zn] 0 /[3-F-Py] 0 /[L-ML] 0 , 50 equiv of L-manOCA can be smoothly converted to polymer with a conversion of 83% in 30 min with toluene as a solvent at room temperature (Table 1, entry 1, [Zn] 0 = 2[complex 1]).…”

Highly Regioselective Ring-Opening Polymerization of Cyclic Diester for Alternating Sequence-Controlled Copolymer Synthesis of Mandelic Acid and Glycolic Acid

“…Finally, the polymer chain structure becomes RO-MA-GA-(MA-GA) n -Zr or RO-(GA-MA) x -(MA-GA) y -Zr, and an alternating copolymer structure is achieved. Other complexes, for example, the zinc-BDI complex 46 and yttrium phenoxide 47 utilized for the ROP of rac-PDD do not show high regioselectivities (Table S1 and Figure S10). Although some similar zirconium complexes with more bulky substituted groups of amantadinyl show low activities, their regioselectivities are similar to that of zirconium complex 1a (Table S1 and Figures S11 and S12).…”

Direct carbon capture for production of high-performance biodegradable plastic by cyanobacterial cell factory

“…Samples were resuspended in chloroform and filtered through a 0.4 μm filter. The MALDI-TOF mass spectrum was carried out using the DCTB as a matrix, CF3CO2Na as a cationization agent and chloroform as a solvent in a MALDI-7090 (SHIMADZU, Japan) mass spectrometer 12 .…”

“…4C, the molecular weight of PLA was determined by GPC and MALDI-TOF mass spectroscopy (Fig. S3) 12 . From the GPC spectrum analysis, the average molecular weight (Mw) was found to be 62.5 kDa, and the molecular weight distribution ranged from 2 kDa to 100 kDa (Fig.…”