Synthesis, Characterization and Structural Determination of Lithium and Magnesium Complexes Stabilized by New Ancillary Bulky Ligands BCP from Application of Lactide Polymerization: Nanostructure and Nanotemplate from Self-Assembly of Biodegradable Block Copolymers

Novel and soluble coordinated lithium aggregates have been synthesized and structurally well characterized. They are often electron deficient and are usually multinuclear-multiligand entities hold together by mu-type of bonds. Factors affecting their aggregation will be discussed in details. The reaction of [(EDBP)Li2]2[(nBu)Li(0.5Et2O)]2 (1) (EDBP-H2: 2,2'-ethylidene-bis(4,6-di-tert-butylphenol)) with one equivalent of ROH in toluene gives [(EDBP)Li2]2[(OR)Li]2 (2: R = Bn; 3: R = CH2CH2OEt; 4: R = nBu). In the presence of three equiv THF, the hexa-nuclear compound 1 slowly decomposes to an unusual penta-nuclear lithium complex, [(EDBP)2Li4(THF)2][( nBu)Li] (5). Further reaction of 5 with ROH gives [(EDBP)2Li4(THF)3][(OR)Li] {R = Bn (6), nBu (7), CH2CH2OEt (8)} without a drastic change in its skeleton. Compounds [(EDBP)Li2(HMPA)2][(OBn)Li(HMPA)] (9), [(EDBP)2Li4(THF)][(OCH2CH2OEt)Li]2 (10) and [(EDBP)2Li4(OCH2CH2OEt)(HMPA)]-[Li(HMPA)4]+ (11) (HMPA: hexamethylphosphoramide) can be obtained by the reaction of lithium alkoxide 2, 3 and 4 with “oxygen-donor solvent,” such as THF and HMPA respectively, to gives rearranged and solvated products. Among them, compound 8 has shown great reactivity toward ring-opening polymerization of L-lactide yielding polymers with very low polydispersity indexes in a wide range of monomer-to-initiator ratios. The reaction of 1 with 2 equiv of 2,4,6-trimethylacetophenone in toluene can also obtain a lithium enolate 12 without any drastic change in skeleton. In the presence of excess THF furnishes a lithium enolate, 13, without EDBP backbone. Compound 12 represents the first example of a well-defined lithium enolate initiator for highly isoselective polymerization of MMA under relatively mild reaction conditions. Besides, four novel lithium and magnesium complexes, [(EDBPBS)2Li2(THF)] (16); [(EDBPBS)Li(THF)2] (17); [(BHPMP-TS)Mg(THF)]2 (18); [(BHPMP-TS)2Mg2(THF)3]2 (19), stabilized by two new ancillary ligands (EDBP-BS: 2,4-di-tert-butyl-6-(1-(3,5-di-tert-butyl- 2-hydroxyphenyl)ethyl)phenyl benzenesulfonate; BHPMP-TS: 4-tert-butyl-2,6-bis(3,5-di-tert-butyl-2-hydroxybenzyl)phenyl-4-methyl- benzenesulfonate. In the presence of THF, 17 and 18 can also be prepared directly by 16 and 19 respectively, followed by rearrangement and solvation. More importantly, a combination of free radical polymerization and ring-opening polymerization of lithium alkoxide macroinitiator enables us to synthesize block copolymer, PS-b-PLLA. According to the results of TEM, SAXS and FESEM, these block copolymers show a well-defined material system with self-assembling nanostructures, including sphere, hexagonal cylinder, lamelle and hexagonally packed nanohelix.Contents Abstract…………………………………………………………………....1 Chapter 1. Introduction Biodegradable Polymers……………………………………...3 Metal Complexes Supported by Salen Ligands………………7 Metal Complexes Supported by Biphenolate Ligands………..9 References…………………………………………………...13 Chapter 2. Synthesis, Characterization and Structural Determination of Polynuclear Lithium Aggregates and Factors Affecting Their Aggregation Introduction……………………………………………………17 Results and Discussion………………………………………19 Synthesis and characterization of Mixed-Ligand Lithium Aggregates……………………………………………………19 Synthesis and characterization of Lithium Enolate Complexes…………………………………………….…….22 Molecular Structure Studies of 5, 12 and 13…………….…..24 Ring-Opening Polymerization of L-Lactide Using Complex 8 as an Initiator………………………………………………..28 Anionic Polymerization of MMA Using Complexes 12 as Initiator……………………………………………………...31 Summary………...…………………………………………....32 Experimental Section………………………………………....33 References…………………………………………………….38 Chapter 3. Synthesis, Characterization and Structural Determination of Lithium and Magnesium Complexes Stabilized by New Ancillary Ligands Introduction………………………………………………….45 Results and Discussion………………………………………52 Synthesis and characterization of p-substituted- benzenesulfonylate ligands………………………………....52 Synthesis and characterization of lithium and magnesium complexes supported by EDBP-BS and BHPMP-TS ligands……………………………………………………...53 Molecular Structure Studies of 16-19………………………55 Summary…...…………………………………………..…....59 Experimental Section…………………………………..…....60 References………………………………..………...………..63 Chapter 4. BCP from Application of Lactide Polymerization: Nanostructure and Nanotemplate from Self-Assembly of Biodegradable Block Copolymers Introduction………………………………………………….68 Preparation of 4-Hydroxyl-TEMPO-terminated Polystyrene………………………………………………….71 Synthesis of Polystyrene-Poly(L-lactide) Diblock Copolymer…………………………………………………..73 Morphologies of PS-b-PLLA……………..………..……....80 Summary………………………….…..……………………..85 Experimental Section………………………………………..86 References…………………………………………………...87 Chapter 5. Conclusion………………………………………………….90 Chapter 6. General Informations NMR Spectra…………………………………....………….92 Gel Permeation Chromatography (GPC)……………….…..9