|M.Sc Student||Shpasser Dina|
|Subject||Zinc Based Organometallic Complexes for the Polymerization|
of Polar Monomers and Synthesis of
Functional Cyclic Di-ester Monomers
|Department||Department of Chemistry||Supervisors||Professor Moris Eisen|
|Professor Emeritus Noah Lotan|
Aliphatic polyesters are an attractive alternative to current oil-based plastics because they are biodegradable, decompose into nontoxic by-products and can be derived from natural resources. Polyesters containing functional groups connected to the main polymer chain are necessary for some applications. Introduction of functional groups within the polymer chain is achieved by polymerizing monomers containing the functional group.
We present the synthesis of two monomers with a di-ester backbone bearing a functional group. One of the monomers 3,6-dimethyl-3,6-bis-(3-oxo-butyl)-[1,4]dioxane-2,5-dione was previously synthesized by Nicolaou et al. as one of the materials in a multi-step synthesis. Interestingly, when the dry conditions required for the synthesis were not vigorously observed a tri-cyclic product containing four, five and six membered rings was obtained.
The other monomer is a newly synthesized monomer [2-(3,6-dioxo-[1,4]dioxan-2-yl)-ethyl]-carbamic acid tert-butyl ester. The first product, (S)-4-tert-butoxycarbonylamino-2-hydoxy-butyric acid, in the multi-step synthesis of the monomer gave different NMR spectra in D2O and CDCl3. We investigated and found that (S)-4-tert-butoxycarbonylamino-2-hydoxy-butyric acid existed in two conformations in CDCl3 and in only one conformation in D2O. Polymerization of the obtained monomer with Ti(OiPr)4 gave a polymer with Mn=5,700.
In the industry today, tin compounds are used for the bulk polymerization and co-polymerization of lactide. Tin compounds have the disadvantage that they are cytotoxic. As a result, continuous efforts have been devoted to the development of new initiators and catalysts containing non-toxic metals, among these metals is zinc.
We synthesized a new zinc based organometallic complex LZnOiPr. L=2-((2,5-di-tert-butylphenyl)amino)-4-((2,5-di-tert-butylphenyl)imino)-2-pentene. Polymerization of lactide at 60°C for 48 h using the zinc catalyst synthesized gave a polymer with Mn=28,800.