Ring Opening Polymerization of Lactides and Lactones by Multimetallic Titanium Complexes Derived from the Acids Ph2C(X)CO2H (X = OH, NH2)

Abstract

The reactions of the titanium alkoxide [Ti(OR)4] (R = Me, nPr, iPr, tBu) with the acids 2,2’-Ph2C(X)(CO2H), where X = OH and NH2, i.e., benzilic acid (2,2’-diphenylglycolic acid, L1H2), and 2,2’-diphenylglycine (L2H3), have been investigated. The variation of the reaction stoichiometry allows for the isolation of mono-, bi-, tri or tetra-metallic products, the structures of which have been determined by X-ray crystallography. The ability of the resulting complexes to act as catalysts for the ring opening polymerization (ROP) of ε-caprolactone (ε-CL) and r-lactide (r-LA) has been investigated. In the case of ε-CL, all catalysts except that derived from [Ti(OnPr)4] and L2H3, i.e., 7, exhibited an induction period of between 60 and 285 min, with 7 exhibiting the best performance (>99% conversion within 6 min). The PCL products are moderate- to high-molecular weight polymers. For r-LA, systems 1, 3, 4 and 7 afforded conversions of ca. 90% or more, with 4 exhibiting the fastest kinetics. The molecular weights for the PLA are somewhat higher than those of the PCL, with both cyclic and linear PLA products (end groups of OR/OH) identified. Comparative studies versus the [Ti(OR)4] starting materials were conducted, and although high conversions were achieved, the control was poor.

Reaction of Ph2C(X)(CO2H) (X = OH, NH2) with [VO(OR)3] (R = Et, nPr): structure, magnetic susceptibility and ROP capability

“…3 New ROP catalysts based on titanium, lithium, zinc, aluminium, and rare-earth metals incorporating the motif Ph 2 C(X) were reported, together with a number of intriguing molecular structures. 4 Recently, for the group V metals, we have investigated the use of niobium and tantalum alkoxide precursors, which afforded tetranuclear complexes [M 4 (OEt) 8 (L 1 ) 4 (μ-O) 2 ] in the case of benzilic acid (L 1 H 2 ), and dinuclear complexes [Nb 2 (OEt) 4 (L 2 H 2 ) 4 (μ-O)] in the case 2,2′-diphenylglycine (L 2 H 3 ). 5…”

Tri-Layer Core–Shell Fibers from Coaxial Electrospinning for a Modified Release of Metronidazole

“…From the figure, it can be significantly observed that the drug MTD has several obvious diffraction peaks at 2θ from 5 • to 40 • , which are 12.4 • , 14.1 • , 18.2 • , 25.5•, and 27.9 • , respectively, which indicates that the drug MTD has crystalline properties and pure MTD exists in crystalline form. PCL is also crystalline[90], but is semi-crystalline in nature, with a small peak at 2θ at 22.6 • . The XRD images for PVA and other raw materials are amorphous, as indicated by the XRD images of PVA and other raw materials which are relatively smooth and have no obvious diffraction peaks.…”