Preparation of multiblock copolymers via step-wise addition of l-lactide and trimethylene carbonate

Abstract

The synthesis of up to pentablock copolymers from various combinations of l-lactide and trimethylene carbonate was accomplished using a dinuclear zinc complex, and the physical, thermal, and mechanical properties of the resulting copolymers evaluated.

Exploring Oxidation State-Dependent Selectivity in Polymerization of Cyclic Esters and Carbonates with Zinc(II) Complexes

“…We previously described the preparation and investigation of the solution state behavior of [(fc P,B )Zn(μ-OCH 2 Ph)] 2 ( Abubekerov et al., 2018 ). Our studies revealed that this compound retains its dimeric state before and during the ring-opening polymerization of LA and TMC.…”

“…However, after the reaction onset, the signals corresponding to (fc P,B )Zn(OPh) do not shift in the 1 H NMR spectra ( Figure S24 ); this finding prompted a further look into the polymerization process by diffusion ordered spectroscopy. We previously used this technique to illustrate that our zinc polymerization systems show the same diffusion rate for the catalyst and the polymer ( Abubekerov et al., 2018 ). However, in the present case, the diffusion rate of polylactide (PLA) was substantially different from that of (fc P,B )Zn(OPh), suggesting that (fc P,B )Zn(OPh) does not participate in the polymerization process ( Figure S26 ).…”

“…We previously reported a computational study comparing the energies of possible monomeric and dimeric structures of the zinc benzoxide complexes and showed that the dimer [(fc P,B )Zn(μ-OCH 2 Ph)] 2 was more stable (by 3.3 kcal/mol) than the corresponding monomer (fc P,B )Zn(OCH 2 Ph) ( Abubekerov et al., 2018 ). Calculations conducted at the same level of theory showed that, in the oxidized state, the dimeric species [(fc P,B )Zn(μ-OCH 2 Ph)] 2 2+ was also greatly favored (20.1 kcal/mol) over the corresponding monomer ( Figure 5 ).…”

“…In this case, the oxidation of the ligand could result in the loss of the zinc-phosphine interaction, similar to redox-switchable hemilabile ligands, and in altering the reactivity of a catalyst. Recently, we described the preparation as well as the characterization of [(fc P,B )Zn(μ-OCH 2 Ph)] 2 ( Abubekerov et al., 2018 ). However, in the case of the reduced species, a direct zinc-phosphine interaction was not observed.…”

Switchable Ring‐Opening Polymerization by a Ferrocene Supported Aluminum Complex

“…It is unusual for metal complexes to be able to ring open TMC in the presence of LA, due to a strong 5‐membered ring metal lactide‐coordination‐insertion intermediate, but we attempted to study this reaction further given the success in synthesizing the (PTMC/PLA)‐PCHO‐PLA‐O i Pr block copolymer. First, LA was polymerized to a near full completion, which required heating for 4 days at 100 °C (Table , entry 6).…”