Metal Catalysts And Organocatalysts For Olefin Polymerization And Ring-opening Polymerization

Metal catalysts and organocatalysts are widely used in olefin polymerization as well as ring-opening polymerization.Present thesis is divided into the four main parts.1.Camphor-based phosphine-carbonyl ligands for Ni catalyzed ethylene oligomerization was discussed.In this section,Ni and Pd complexes based on camphor-based phosphine-carbonyl ligands containing biaryl moieties were synthesized and thoroughly characterized.The incorporation of biaryl moieties to the structure of the ligands can increase the molecular weight of the polymers upon creation of the Ni-Ar intermolecular interactions.The camphor backbone was used to introduce alkyl groups with electron donating properties to the carbonyl side of the structure.Moreover,the rigid bridge-ring of the camphor structure can effectively inhibit the rotation of the PC-CO bond.It has been reported that the cyclic alkane linker can prevent the rotation of the PC-CS bond in the phosphine-cyclopentanesulfonate of Ni based catalyst system that leads to the production of high molecular weight polyolefins.Herein,a similar strategy was used to improve the performance of the Ni catalyst system containing phosphine-carbonyl ligands.2.A series of phenoxyimine ligands bearing different nitrogen-containing second coordination spheres for zinc and aluminum complexes for the ring opening polymerization of the cyclic esters(such as rac-LA,?-caprolactone(CL),?-valerolactone(VL),and trimethyl carbonate(TMC))were designed,investigated,and comprehensively analyzed.The stereoselectivity of the mentioned zinc and aluminum complexes supported by the phenoxyimine ligands on the ring opening polymer:ization of the rac-LA and copolymerization of the rac-LA with the CL and VL monomers using aluminum catalyst complexes were investigated.It was reported that the ligands with open nitrogen donors lead to the dynamic NNO-chelates with high interactions of nitrogen-metal coordination.The zinc catalyst complex with the bulky triphenylsilyl located at the 3-position of the phenoxy could produce highly heterotactic polymers(PLAs)at either room and low temperatures through its highly stereoselectivity during ROP of the rac-LA.Moreover,homopolymerization of the rac-LA cyclic monomers and their copolymerization with the LC and LV monomers were successfully done at high temperatures by the aluminum catalysts.3.A series of ?-imino-ketone nickel catalysts as a versatile platform for generation of branched polyolefins with high molecular weight were thoroughly investigated.The catalysts with specific properties such as facile synthesis and modification,high thermal stability,and high activity even without the addition of cocatalysts during the olefin polymerization were introduced as a potential structure for(co)polymerization process.These catalysts were successful to produce high branched polymers with high molecular weights polyethylene as well as copolymerization of the ethylene with a series of the polar monomers.The versatility of the produced nickel catalyst with aforementioned ligand platform could pay the way for the formation of the dinuclear counterpart and also installation of an anchor for heterogenization of the catalyst.4.The sidearm effect in(thio)urea/alkoxide mediated ROP of cyclic esters was investigated.herein,a series of(thio)ureas bearing 2-,3-and 4-pyridyl were synthesized,respectively.The 2-pyridyl group can form an intramolecular coordination bond with the alkali metal ion coordinated with the S/O atom,indicating a sidearm effect.Moreover,the possibility of the Lewis acid/base modulation on the sidearm group in(thio)urea/alkoxide mediated switchable ring-opening polymerization was investigated.