Sumários
Exercises and doubts about Coordination Polymerization and Chemical Reactions in Polymers. Preparation to the first MAP45.
12 março 2025, 09:00 • Pedro Gomes
Solving exercises no. 1 to 7 of the PDF entitled "Coordination Polymerization + Chemical Reactions in Polymers"
Doubts: preparation to the first MAP45.
Exercises and doubts about Controlled Radical Polymerization, Anionic Polymerization and Cationic Polymerization. Preparation to the first MAP45.
11 março 2025, 12:00 • Pedro Gomes
Solving exercises no. 2, 3, 4, 5 and 6 of the PDF entitled "Controlled Radical Polymerization + Anionic Polymerization + Cationic Polymerization"
Doubts: preparation to the first MAP45.
Chemical Reactions in Polymers. Natural Polymers.
6 março 2025, 14:00 • Pedro Gomes
Chemical Reactions in Polymers:
Functional group reactions.
Ring formation reactions (in the polymer backbone).
Crosslinking reactions.
Block and graft copolymer formation.
Polymer degradation.
Natural Polymers:
Polysaccharides of vegetal origin (cases): Cellulose, Amylose and Amylopectin. Polysaccharides of animal origin (cases): Chitin, Chitosan and Glycogen.
Modifications of cellulose (cases): Cellulose xanthate (viscose rayon textile fibres); Cellulose acetate (rayon acetate textile fibres); Cellulose nitrate (plastics, lacquers, explosives); Hydroxyethyl Cellulose (emulsifiers, shampoo thickeners).
Natural Rubber: from Gutta Percha tree (thermoplastic - trans-1,4-isoprene), from Hevea Brasiliensis tree and Guayule bush (elastomer - cis-1,4-isoprene).
Polypetides (Proteins).
Nucleic Acids.
Quiz 7.
Chain-Growth Polymerization (cont.): Coordination Polymerization
5 março 2025, 09:00 • Pedro Gomes
Coordination Polymerization:
- 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.
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.
Copolymerization of olefins with ansa-metallocene catalysts.
- 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.
Quiz 6.