A Highly Efficient Initiator for the Ring-Opening Polymerization of Lactides and ε-Caprolactone:  A Kinetic Study

Abstract

A trinuclear zinc alkoxide [{(BDI-OMe)Zn(μ-OBn)}2Zn(μ-OBn)2] (1) and a homoleptic zinc complex [(BDI-OMe)2Zn] (2) have been prepared by the addition of benzyl alcohol to a mixture of BDI-OMe-H with Et2Zn. Compound 1 has been employed as an initiator for ring-opening polymerization of lactides and ε-caprolactone. The highly efficient initiator of the zinc complex shown in the polymerization process enabled us to synthesize the PLA at ambient temperature, yielding PLA with well molecular control and narrow molecular weight distribution in a very short period of time. The polymerization kinetics were studied with [LA]0/[1] = 200/1 and [LA]0 = 0.5 M at 25 °C. Experimental results indicate a second-order dependency on [LA] (k obs = 0.033 M-1 s-1). Moreover, a first-order dependency in [1] is indicated of k obs vs [Initiator], with a slope equal to the first-order rate constant k = 12.2 M-2 s-1. Furthermore, the heterotactic PLA with Pr up to 83% can be achieved in a mixed solvent of CH2Cl2 and THF at −35 °C. However, according to polymerization kinetic studies of CL, a first-order dependency on [CL] and [1] is observed for ROP of ε-caprolactone.

Coordination Chemistry and Reactivity of Zinc Complexes Supported by a Phosphido Pincer Ligand

“…Presumably, 3 is produced by a very slow ligand-exchange reaction of 2 (Scheme 2). [37] Formation of homoleptic L 2 Zn complexes has been reported for undemanding and/or with poorly electron donating bidentate ligands, [25,38,39] but it is definitely uncommon for complexes bearing tridentate ligands. Generally, the presence of a bulky chelating ligand around the Zn center inhibits the disproportion reaction.…”

“…[30] Alternatively, the PPP ligand may employ only one neutral phosphine donor for coordination to the metal center, resulting in an anionic bidentate ligand. Although three-coordinate zinc phosphine complexes are extremely rare, [25,38,39,43] the bis-chelated zinc species featuring the k 2 -PPP ligand were successfully optimized. In these species, the zinc atom is in a trigonal-planar environment (sum of the bond angles: 359.9 and 360.08 for the alkyl and the amide derivative, respectively), coordinated by two phosphorus atoms to form a five-membered chelate ring.…”

“…This behavior is uncommon, since polymerization of e-CL is frequently faster than that of lactide, although some exam- www.chemeurj.org ples of zinc complexes with opposite reactivity towards these two monomers have been recently reported. [25,52] The influence of solvent on the polymerization of l-lactide was also investigated. The productivity was slightly improved when the polymerization was performed in a more polar solvent, such as dichloromethane ( Table 2, run 14).…”

Characterization of Polylactide-Stabilized Gold Nanoparticles and Its Application in the Fabrication of Electrochemical DNA Biosensors

“…19 Earlier research has reported that stabilization of AuNPs takes place between the carboxylic groups of polymer matrix. 20 Practically, the application of screen-printed carbon electrode (SPCE) as a disposable sensor for detection of DNA hybridization is attractive since it allows low-cost electrochemical biosensor. PLA-stabilized AuNPs modified electrodes have been described previously as successful and practical sensor identifying As III and sulfide in water.…”

A novel initiating system for ring‐opening polymerization of ε‐caprolactone: Synthesis of triarm star‐shaped poly(ε‐caprolactone)

“…1 Many catalysts such as stannous, 2,3 calcium, 4,5 aluminum, 6,7 and zinc [8][9][10] compounds have been developed to prepare PCL by ring-opening polymerization (ROP) of e-caprolactone (CL). PCLs with complex macromolecular architectures have attracted great attention in relation to functional materials.…”