Chain-Growth Polymerization (cont.). Coordination Polymerization.

19 abril 2022, 11:30 • Pedro Teixeira Gomes

- Polymerization of Olefins (insertion): Monomers (olefins, dienes e cycloolefins). Commodity polyolefins (physical and production features of low density polyethylene (LDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE) and polypropylene (PP). Ziegler-Natta catalysts: definition. First, second and third generation Ziegler-Natta catalysts. Phillips catalysts. Homogeneous Ziegler-Natta catalysts: metallocenes; MAO (methylaluminoxane) cocatalysts. Role of the MAO cocatalyst. General mechanism of Ziegler-Natta catalysis. Ziegler-Natta stereospecific catalysts and ansa-metallocene catalysts. Isospecific and syndiospecific ansa-metallocenes. General features of metallocenic polyolefins.

- Polymerization of Dienes (insertion): 1,4-cis-polybutadiene (synthetic rubber), 1,4-trans polybutadiene and 1,2-polybutadiene; 1,4-cis-polyisoprene (natural rubber and synthetic natural rubber) and 1,4-trans-polybutadiene. Stereospecific catalysts: 1) Ziegler-Natta e 2) Allyl complexes (without Al cocatalysts). Allyl Ni catalysts: influence of the addition of a phosphine. Stereoregulating mechanism.

- Ring Opening Metathesis Polymerization (ROMP): Reaction of ring-opening metathesis. Type of monomers (cycloolefins and cycloalkynes). Catalysts: 1) Ziegler-Natta catalysts and 2) well-defined catalysts (metal carbenes). ROMP mechanism. Examples of polymers and copolymers obtained from the ROMP polymerization of a single cyclomonomer.

- Ring Opening Polymerization (ROP): Monomers (epoxides, cyclic lactams, cyyclic lactone, cyclic dilactones, N-carboxyanhydrides, cyclic carbonates,  cyclic siloxanes). Catalysts (alkyl and alkoxide transition metal and main-group metal complexes). Synthesis of polyethers. Synthesis of polyamides and polyesters. Synthesis of streoregular poly(lactic acid) (PLA). Synthesis of polycarbonates, polypeptides and silicones.

- Modes of initiation of most general monomers (summary): Free radical, Cationic, Anionic and Coordination.